Category Solar Efficiency

Even if silicon is actually the industry common semiconductor in the majority of electric products, including the solar cells that photovoltaic panels employ to convert sunshine into electricity, it is not really the most effective material readily available. For instance, the semiconductor gallium arsenide and related compound semiconductors offer practically two times the performance as silicon in solar units, however they are rarely utilized in utility-scale applications because of their high production value.

University. of Illinois. teachers J. Rogers and X. Li discovered lower-cost ways to produce thin films of gallium arsenide which also granted usefulness in the types of units they might be incorporated into.

If you can minimize substantially the cost of gallium arsenide and other compound semiconductors, then you could increase their variety of applications.

Typically, gallium arsenide is deposited in a single thin layer on a little wafer. Either the desired device is produced directly on the wafer, or the semiconductor-coated wafer is cut up into chips of the preferred dimension. The Illinois group chose to put in multiple levels of the material on a one wafer, making a layered, “pancake” stack of gallium arsenide thin films.

Figure 1 Thin Film Solar
Source: University of Illinois

If you increase ten levels in one growth, you only have to load the wafer once saving substantially on production costs. Current production processes may require ten separate growths loading and unloading with heat range ramp-up and ramp-down adds to time and costs. If you take into account what is necessary for each growth – the machine, the procedure, the time, the people – the overhead saving derived though the new innovative multi-layer approach, a substantial cost reduction is achieved.

Next the scientists independently peel off the levels and transport them. To complete this, the stacks alternate levels of aluminum arsenide with the gallium arsenide. Bathing the stacks in a solution of acid and an oxidizing agent dissolves the layers of aluminum arsenide, freeing the single thin sheets of gallium arsenide. A soft stamp-like device picks up the levels, one at a time from the top down, for shift to one other substrate – glass, plastic-type or silicon, based on the application. Next the wafer could be used again for an additional growth.

By doing this it’s possible to create considerably more material much more rapidly and much more cost effectively. This process could make mass quantities of material, as compared to simply the thin single-layer way in which it is usually grown.

Freeing the material from the wafer additionally starts the chance of flexible, thin-film electronics produced with gallium arsenide or many other high-speed semiconductors. To make products which can conform but still retain higher performance, which is considerable.

In a document published online May 20 in the magazine Nature the group explains its procedures and shows three types of units making use of gallium arsenide chips made in multilayer stacks: light products, high-speed transistors and solar cells. The creators additionally provide a comprehensive cost comparability.

Another benefit of the multilayer method is the release from area constraints, specifically important for photo voltaic cells. As the levels are removed from the stack, they could be laid out side-by-side on another substrate to create a significantly greater surface area, whereas the typical single-layer process confines area to the size of the wafer.

Figure 2 Solar Arsenium
Source: University of Illinois

For solar panels, you want large area coverage to catch as much sunshine as achievable. In an extreme situation we could grow adequate levels to have ten times the area of the traditional.

After that, the team programs to explore more potential product applications and additional semiconductor resources that might adapt to multilayer growth.

About the Source – Shannon Combs publishes articles for the residential solar power savings web log, her personal hobby weblog focused on recommendations to aid home owners to save energy with solar power.

Rising inventory levels of photovoltaic (PV) panels and new production capacity coming online is driving solar PV prices lower and thereby, bringing solar energy closer to grid price parity. With the release of the latest earnings of solar energy companies, Wall Street’s keen attention to revenue guidance, inventory levels and pricing are paramount in diagnosing the health of the solar energy industry. Expectations call consolidation of the solar industry with some key players gaining market share and for others it becomes more challenging. However, despite the turbulence in the industry, consumers will benefit in the near-term as solar PV prices fall and government incentive fuel growth in solar PV deployment.

To get a better perspective on the solar PV industry, let’s examine inventory levels for some of the leading solar PV suppliers. The following chart, Figure 1, compares inventory levels in relationship to sales volume. While inventory levels have increased, the level of inventories to sales is not egregious

Figure 1 Sales and Inventory levels

While it is important to control inventory levels in relationship to sales, revenue growth is predicated upon price, performance, and return on investment for prospective customers. Thin-film PV has emerged as the low-cost solar solution even with its lower efficiency levels in comparison to mono-and poly-crystalline PV panels. Thin-film still offers a lower cost/watt than crystalline PV, see Solar Shootout in the San Joaquin Valley , but prices for crystalline PV are falling as a result of rising production capacity and inventory levels.

Figure 2 Market Value

In Figure 2 Green Econometrics is comparing the market value of some of the leading PV suppliers as measured by their respective stock prices. In the valuation of solar PV suppliers, the stock market appears to be betting heavily on thin-film PV, as First Solar (FSLR), the leading thin-film PV supplier, enjoys a market value that accounts for over half the value of the entire solar industry. FSLR is positioned as the low-cost supplier in the solar industry with its announcement of $1 per Watt reducing its production cost for solar modules to 98 cents per watt, thereby braking the $1 per watt price barrier. However, new panel suppliers, mainly from China are pushing prices lower for poly-and mono-crystalline panels suppliers. ReneSolar (SOL) is seeing average selling prices for wafers at $0.93 per watt and bring PV panels prices to under $2.00 per watt.

There appears to be a lot riding on the success of thin-film PV and as prices fall for crystalline PV, the closer we get to grid parity. In the following chart, Figure 3, price for crystalline PV have declined quite dramatically in the last 30 years. According to the Energy Information Administration, in 1956 solar PV panels were $300 per watt, and in 1980, the average cost per solar modules was $27/watt and has fallen precipitously to approximately $2/watt in October 2009. As the installed cost of solar PV falls closer to $4/watt, pricing per kilowatt-hour (KWH) (depending on your climate and geography), equates to approximately $0.16/KWH that would be inline with utility rates after rates caps are removed.

Figure 3 Solar PV Prices

The bottom line is that despite the lower PV panel costs; we are still not at parity with hydrocarbon fuels such as coal and oil. Carbon based taxes or renewable energy incentives as well as more investment into alternative energy should improve the economics of solar and wind and bring us to grid parity.

Last month First Solar (FSLR) achieved a milestone in the solar industry with its announcement of $1 per Watt reducing its production cost for solar modules to 98 cents per watt, thereby braking the $1 per watt price barrier.. While the achievement is great news for the solar industry some studies suggest more work is needed. An article in Popular Mechanics $1 per Watt talks of university studies questioning the scalability of solar given the immense global needs for energy. Last year our post included an article Solar Energy Limits – Possible Constraints in Tellurium Production? discussing possible limits on tellurium production on thin film solar photovoltaic (PV) suppliers.

In addition, Barron’s published an article (March 30, 2009)_ Nightfall Comes to Solar Land providing unique insight into the economics of solar PV suppliers. High oil prices and soaring stock prices on solar PV companies fueled silicon suppliers to ramp production capacity that has now transitioned, according to the Barron’s article, into an over supply of polysilicon used in the production of PV panels and subsequently, eroding the cost advantage established by thin film PV companies such as First Solar and Energy Conversion Devices (ENER) over polysilicon PV firms such as SunPower (SPWRA).

However, the PV panels typically represent approximately half the cost of a solar energy system. The following figure, Solar Installation Costs compares the total cost of installing a solar energy system which includes labor and supporting matertials.

Figure 1 Solar Installation Costs

As illustrated in Figure 1, the panels represent a significant cost of installation, but the labor and support brackets for the PV panels are significant as well. While thin film PV enjoys significantly lower panel costs and is easier to install, the supporting brackets are sometimes more expensive. As prices for silicon fall, the cost disparity between thin film and silicon PV will narrow.

Figure 2 Solar Energy Economics

In Figure 2 Green Econometrics is comparing PV efficiency as measured by watts per square meter versus cost per watt. The selected companies represent a small portion of the global PV suppliers, but do illustrate the position of the leading US suppliers. The ideal model is to lower cost per watt while improving PV efficiency. But be cognizant that PV module cost per watt may not be indicative of the total system costs.

A comparison of wind and solar energy costs is demonstrated by Detronics and offers a useful framework to compare wind and solar costs by kilowatt-hour (KWH). As a caveat, wind and solar resources will vary dramatically by location. In the Detronics example, the costs per KWH represent the production over one year and both wind and solar have 20-year life spans. Over twenty years the 1,000-watt wind systems cost per KWH of $7.35 would average approximately $0.36 per KWH and the 750-watt solar systems cost of $10.68 would amount about $0.53 per KWH over the investment period.

Figure 3 Alternative Energy Pricing

The Alternative Energy Pricing chart was base on research from Solarbuzz which is one of the leading research firms in solar energy. The cost per KWH that Solarbuzz provides is a global average. Even with cost per watt falling below $1.00, the system costs after installation are closer to $5.00 according to Abound Solar (formerly known as AVA Solar) and is still higher than parity with grid with a cost of $0.21 per KWH.

The bottom line is that despite the lower PV panel costs; we are still not at parity with hydrocarbon fuels such as coal and oil. Carbon based taxing or alternative energy stimulus and more investment into alternative energy is required to improve the economics of solar and wind.

As energy and food prices set new world records, what can we do at home to avert the crisis? Food prices are rising because corn is diverted from food production to producing ethanol for use as fuel in motor vehicles and is exacerbated by the recent flooding in the Mid West. Oil prices continue to escalate as demand for oil in developing countries increases and supply constraints, rising production costs, and limited refining capacity constrain the supply of oil. These factors continue to weigh against homeowners that will face escalating fuel bills to heat or cool their homes. There are some viable alternative energy solutions including wind and solar as well as home insulation that should offset the rising cost of energy. As far as food for fuel, we need to break our dependence on hydrocarbons which continues to impact our climate and weather and transfer our wealth to oil producing nations

Corn Prices have increased 264% since 2005. The rising price of corn used for ethanol is causing farmers to plant more corn and less production of other grains such as wheat or soy. Lower supply of grains is driving up food prices. Rising food prices is most debilitating to the poor, especially those in developing countries.

Figure 1 Corn Prices

Growing demand for oil and questions over Peak Oil suggesting even with oil prices rising to such an elevated level, production is rather anemic. According to the Energy Information Administration (EIA) , while oil prices increased 344% since 2001, oil production from OPEC is up only 1.2% over this same period.

Figure 2 Oil Prices

According to the EIA The demand for oil in China is growing at an 8.1% CAGR over the last five years. With demand for oil growing significantly in developing countries and despite production developments in Saudi Arabia and the 5-to-8 billion deepwater Tupi oil discovery in over Brazil The Tupi announcement in January 2008 is the world’s biggest oil find since a 12-billion-barrel field discovered in 2000 in Kazakhstan according the International Herald Tribune. These new oil discoveries are often in inhospitable areas or deep ocean environments, which makes extraction costly and difficult.

Figure 3 Rig Count and OPEC Oil Production

What can we do? . Forget drilling for more oil, electric vehicles and investment into alternative energy is the only way to avert this crisis. OPEC area drilling activity is up 48% since 1998 and yet, despite dramatically higher oil prices, up 5 fold since 1998, OPEC oil production increased only 11% over 1998.

Homeowners could begin to deploy energy saving and alternative energy systems. Wind and solar energy could help reduce some of the pain. As consumer embrace hybrids, electric, and fuel cell vehicles, wind and solar should begin to offer a stronger value proposition. Energy saving tips such as compact fluorescent bulbs, on-demand hot water heaters, and thicker home insulation products should help reduce heating and cooling costs.

According to the American Wind Energy Association AWEA a turbine owner should have at least a 10 mph average wind speed and be paying at least 10 cents per Kilowatt-hour (KWH) for electricity. There are electric utility and tax credits available in some areas. There are also questions regarding zoning restrictions, and whether to connect to batteries for energy storage, or directly to your electric utility. Consult the Wind Energy Resource Atlas of the United States Wind Resource Maps to get a better understanding of wind speeds in your area.

Cost wind systems will vary depending on model and installation costs will vary by your location. The Whisper 500 from Southwest Windpower offers electric production of 538 KWK/month at 12 mph (5.4 m/s). The system weighs 155 lb (70 kg) and has blade span of 15 feet (4.5 m) and must be mounted on a tower in cement. At 538 KWH per month, that is enough energy to cover the needs a modest house with conservative electric usage. Small wind systems can range from under $1,000 to over $20,000 with a payback period of approximately five years depending on wind resources and utility rates.

Solar photovoltaic (PV) panels cost an average of $4.80 per watt according to Solarbuzz which is about $0.24 per KWH over a 20 year life of the PV system. With an average output of approximately 10.6-watts/square foot (114 w/m^2), a five KW PV systems would cover 515 square feet (47.8 sq. meters) costing approximately $36,000 before credits and tax benefits and produce about 490 KWH per month. Of course installations costs are extra, but with PV production ramping and new PV suppliers entering the market we can expect costs to decline. Federal and local tax credits as well as selling unused electric to your local utility offers economic value on the margin.

The economic value is expected to increase as costs decline and electric rates increase and we can expect significantly higher utility rates in the near future. The economics of zero carbon emissions is not even measured as a benefit to the consumer. We are just beginning to see the cost impact of extreme weather and climate change.

Consumers should try to ameliorate the rising cost of energy by investing into solar and wind. There are several companies offering complete installation services. Among these include: Akeena Solar (AKNS) in California and The Solar Center in New Jersey.

The bottom line: energy and food prices are creating a crisis for consumers globally and there are several initiatives that could help minimize the pain. In addition, the erratic weather patterns around the world may be just a prelude to climate changes due to the impact of carbon dioxide on climate, which may cost us much more in the long run. Let’s stop the drain of wealth cause by oil and invest into clean and renewable energy solutions.

Solar energy is gaining considerable attention from Wall Street and countries looking to achieve energy independence. Solar energy represents one of the most significant energy solutions to help eradicate our addiction to oil. Despite the tremendous success offered with solar photovoltaic (PV), more research is required to sustain further deployment and achieve energy independence. Some semiconductor materials used to develop photovoltaic devices are scarce and may limit PV from achieving mass penetration. Let’s review the current solar PV market to better understand the dynamics of this market.

Figure 1 PV Production by Year

Figure 1 demonstrates the rapid market growth of solar PV and Solarbuzz is astute to point out some critical data points: cumulative PV deployment is still less than 1% of global electric usage, PV industry faces capacity constraints, and Germany and Spain account for 47% and 23% of total PV deployment in 2007. With the significant growth in both the production and deployment of solar PV devices, the stock price of some of the leading PV suppliers have appreciated dramatically even despite a recent pull back in the beginning of the year.

Figure 2 PV Production of Leading Suppliers

Despite the turbulence on Wall Street in 2008 with the NASDAQ down 14% year-to-date, and Dow Jones Industrial Average down 7.3% YTD, investor appetite for clean technology stocks remains robust. First Solar (FSLR), a leading supplier of thin film solar PV remains in positive territory and is up nearly ten-fold from its IPO in November 2006. Thin film PV offers a cost advantage over traditional crystalline PV cells. PV devices employ various elements with different band gap properties to achieve improving solar efficiencies. (See our post on semiconductor band gaps: What’s Pushing Solar Energy Efficiency?, October 1st, 2007)

Figure 3 Market Capitalization Solar PV Suppliers

There are several elements used in thin film PV production. Among the elements used include cadmium and tellurium (CdTe), copper, indium, and selenium, (CuInSe), and copper, indium, gallium, and selenium (CIGS). These various elements are used to improve operating efficiencies and lower production costs of PV devices. In general, crystalline PV devices have higher solar efficiencies, but cost more due to their material thickness of 200-to-300 microns. Whereas, thin film PV are usually about 3 microns deep offering significantly lower production costs. However, SunPower (SPWR) the leading polycrystalline silicon PV supplier offers the highest solar efficiency a rating of 22.7% that started shipping in 2007.

Figure 4 FSLR and SPWR Solar PV Production

FSLR and SPWR are the two leading PV players as measured by Wall Street in terms of market valuation. The cost-efficiency tradeoff between these two PV suppliers offers an interesting framework to evaluate the solar PV market.

Figure 5 PV Cost-Efficiency

The stock market appears to be betting on FSLR given its market capitalization of $22 billion and trading at 43 times 2007 revenues of $504 million. FSLR employs CdTe in its solar modules. In several postings on Seeking Alpha starting back in November 2007, Anthony and Garcia de Alba have provided valuable insight into material constraints in the production of PV devices.

Tellurium is a rare metalloid element that is used in producing semiconductor materials because it does not conduct electricity. Tellurium is recovered as a by-product in refining and processing of gold and copper as well as other ores. Tellurium was primarily used to create metal alloys that enable easier machining of end products.

Because of its unique properties, Tellurium and cadmium (CdTe) have been used in thin film PV production since the 1980’s. According to a comprehensive study by Fthenakis and earlier work by Moskowitz “The Life Cycle Impact Analysis of Cadmium in CdTe PV Production”, CdTe is deposited on a thin film substrate using electrodeposition, chemical surface deposition, and vapor transport deposition. FSLR reports in their 10K that they employ a proprietary vapor transport deposition process for CdTe PV production.

A thin film of CdTe is deposited on a substrate at a thickness of 3 microns. According to the Fthenakis and Moskowitz, back in the 1980’s, a 10 megawatt (MW) PV facility employing vapor transport deposition of CdTe uses 3,720 kilograms (kg) of CdTe to achieve a10% efficiency at 3 microns. A one-one bond of CdTe with an atomic weight of Cd at 112.41 and Te at 127.60 suggests Te comprises 53% of the weigh of CdTe. With 3,720 kg of CdTe used at 10MW, the amount of Tellurium used is estimated at 1,978 kg or 197.8 kg/MW.

The electrodeposition CdTe process using a mixture of cadmium sulfate and tellurium dioxide used 880 kg of tellurium dioxide, which amounts to approximately 696.8 kg of Te for 10 MW PV productions. The electrodeposition CdTe process would equate to about 69.7 kg of Te per MW. For a 100 MW PV production approximately 7 tons of Te are consumed.

One would assume the PV production process would improve significantly from the 1980’s and the amount of Te consume would decline with improving efficiencies. This would suggest that FLSR at 200 MW PV capacity in 2007 would consume somewhere between 14 and 38 metric tons of tellurium. This figure is significantly higher than the estimates derived from the FSLR tellurium posts on Seeking Alpha that are closer to10 tons per 100 MW (100 kg/MW).

Figure 6 Te Production

Let’s proceed with the conservative figure of 100 kg/MW (10 tons at 100 MW) to assess the tellurium constraints. Tellurium production is a by-product of gold, copper and other ores. We have found Te production estimates ranging from 132 metric tons (MT) to 300 MT per annum. In a National Renewable Energy Laboratory (NREL) report Assessment of Critical Thin Film Resources in 1999 estimated Te production between 200 and 300 metric tons per year in 1997 and indicated under utilization of capacity for the production of tellurium.

Let’s compare our conservative estimate of 100kg/MW Te usage for FSLR to the optimistic production forecast of 300 MT to evaluate capacity constraints for FSLR. With 300 MT (300,000 kg) global Te production and FSLR using 80% of the Te production, capacity of PV tops out at 2,400 MW (2.4 GW).

The U.S. electric energy usage in 2006 was 4,059.91 billion kilowatt hours (KWH) which translates into 463,460 MW (divide 4060 by 365 days x 24 hours). So without significant investment into research and development for PV FSLR could be constrained at 2,400 MW representing only 0.5% of the U.S. electric usage in 2004. Further more, if FSLR were to be constrained at 2.4 GW annual production, revenues ($2.60 per watt Q4/07) would peak at approximately $6.24 billion, a price-to-sales multiple of 3.4x with its market capitalization of $22 billion.

However, in comparison to leading companies in energy, pharmaceuticals, technology and finance, FSLR’s market capitalization is relatively small. Perhaps with improving production processes, FSLR could reduce the amount of Te per panel and improving mining and metal refinement process could increase Te production to expand the market for CdTe thin film PV devices.

Figure 7 Market Capitalization of Leading Companies

The bottom line is that more research and investment into alternative energies is required to ameliorate the world from being held hostage to oil and hydrocarbon fuels that are directly linked to rising CO2 levels and climate change.

Improving economics and high market valuations should help drive research for alternative energy. With the release of Q3/07 financials, it’s clear that the economics of solar photovoltaic (PV) suppliers is improving. Some of the leading pure play publicly traded PV stocks are demonstrating significant improvements in financial performance that should drive further investment into solar and green technology. The improving economics of solar should continue to drive further investment into alternative energy companies as venture capital firms and Wall Street find that alternative energy is a significant secular trend with sustainable economic foundation.

Most visible among the solar PV suppliers is First Solar (FSLR) with y/y revenue growth for Q3/07 increasing 290% and gross margins exceeding 50% and operating margins above 30%. FSLR’s management was clear in articulating that these strong Q3 numbers reflect ramping on of its German manufacturing facility and would not be sustainable. However, with gross margins exceeding 50% and operating margins above 30% Wall Street takes notice and rewards the firm with valuation multiple envious of leading technology companies such as Google (GOOG) and Cisco Systems (CSCO).

Figure 1 Revenues, Margins, and Capacity

The stronger financial performance of solar PV suppliers is significant because it improves the viability of the solar PV business model thereby attracting more investors and in turn drives funding for alternative energy start up companies. FSLR went public in November 2006 with a closing price of $24.74 on its first day. With a closing price one year later of $212.63, FSLR offers investors a yearly return of 759%. The attractive return generated by solar stocks tends to attract more investors and drives market valuations higher thus feeding the flow of additional venture capital funding.

In terms of market valuation FSLR trades at a significant premium to most companies in the S&P 500 as well as leading technology companies including GOOG and CSCO. . Most solar PV companies trade at higher market valuation multiples than CSCO and GOOG. Both FSLR and Sun Power (SPWR) trade at premium price-to-sales (P/S) and price/earnings-to-growth (PEG) multiples in comparison to some leading technology stocks. In terms of PEG ratios, FSLR and SPWR trade at 2.9x and 2.2x respectively while CSCO and GOOG trade at 1.3x and 1.2X, respectively. In comparison, the S&P 500 index trades at a PEG of 0.8x while the technology and energy segments trade at 0.6x and 2.2x, respectively. These high market valuations prove the venture capital community with high exit values on their current crop of alternative energy investments. Please see Figure 2.

It is this premium market valuation multiple that suggests the importance of alternative energy. Wall Street tends to be a leading indicator and keen in its ability to identify secular trends. Major trends command premium valuations and reward venture capital with attractive exist strategies. Wall Street rewards cash flow growth fueling further venture capital funding that in turn, fuels the flow of intellectual and financial capital. The value migration measured by price-to-sales multiples and illustrated by A. Slywotsky in his book Value Migration provide a framework to gauge the significance of trend towards alternative energies. Capital gravitates to the business model that creates economic value and is measured by a stock’s price-to-sale ratio. By that measure solar stocks is where the value is headed.

Figure 2 Price-to-Sales Ratio

The bottom line is that high market valuations attract research funding and brain power. Rising oil prices, rapid industry growth, and high public market valuations of solar PV companies, should act to attract further venture capital funding of alternative energy companies. Increased solar funding should translate into increased research and talent migration that could improve solar efficiency and reduce costs that in turn could bring solar to electric grid parity.

After reviewing some of the details of Honda’s experimental solar-power hydrogen refueling station in Torrance, CA and its fuel cell vehicle several questions concerning efficiency and practicality come to mind. It most be noted that solar and hydrogen don’t emit harmful byproducts such as carbon dioxide or carbon monoxide so both technologies are important to our energy security. First let’s look at the efficiency of hydrogen and second the efficiency of generating hydrogen from solar.

As we learned from science class, hydrogen is the most abundant element in the universe. Hydrogen has approximately 3 times the energy per unit mass as gasoline and requires about 4 times the storage volume for a given amount of energy according to a Hydrogen Energy report from Stanford University. In further review of additional information on hydrogen we are also making some adjustments to our fuel-ranking table.

We are revising Table 1 that was used in our post of October 3, 2007 for data on the energy density for hydrogen from 2.5 kilowatt-hours (KWH) per gallon to 10.1 KWH/gal and is reflected in the revised Table 1 below. The discrepancy lies in measuring the weight of hydrogen in liquid volume. We are calculating the energy density of hydrogen using the high heat values of hydrogen of 61,000 British Thermal Units (BTUs) and a weight 0.57 pounds per gallon from the Stanford Hydrogen Report.

As a reference: 1 KWH = 3,600 kilojoules = 3,412 BTUs

Revised Table 1 Specific Energy, Energy Density & CO2

Hydrogen offers tremendous energy potential, but as we see from Table 1, hydrogen has a low energy density meaning it requires a large storage container to make it practical for use in a motor vehicle. Several car manufacturers including GM and Toyota have developed hydrogen vehicles. Hydrogen can be used in internal combustion engines replacing gasoline or in fuel cells to generate electric to power the vehicle. However, there are some limitations to the current technology that may limit the economic viability hydrogen powered vehicles in the near term. But there are no detrimental emissions with hydrogen as apposed to hydrocarbon fuels thus providing tremendous benefits as vehicle efficiency improves.

Honda’s solar-powered hydrogen fueling station takes nearly a week in sun to produce enough hydrogen to power Honda’s FCX concept hydrogen fuel cell vehicle. Honda employs a Proton Exchange Membrane Fuel Cell (PEMFC) that converts hydrogen to electric that in turn, powers the vehicle. The Honda FCX fuel cell vehicle has two fuel tanks that can be filled with up to 156.6 liters of hydrogen or about 43 gallons that offers 430km (267 miles) driving range. The hydrogen fuel cell vehicle provides a reasonable driving range, but with a fuel efficiency of 6.5 miles per gallon (MPG), suggests more research is needed.

BMW’s Hydrogen 7 can travel 125 miles on hydrogen and 300 on gasoline before refueling. In tests the BMW 745h liquid-hydrogen test vehicle has 75 kg tank has a Hydrogen Fuel Efficiency of 10 km/liter or about 25.2 MPG and cruising speed of 110 MPH. Not too bad for an internal combustion engine that is able to run on gasoline or hydrogen.

Figure 1 Specific Energy

Given the changes to hydrogen’s energy density we are also adjusting hydrogen density (Figure 2) to reflect liquid hydrogen and high-energy value as noted by Hydrogen Properties College of the Desert.

Revised Figure 2 Energy Density: KWH per Gallon

We still have more questions given hydrogen’s very high specific energy, (3 times that of gasoline) and low energy density (4 times the volume of gasoline). Hydrogen is more efficient then petroleum fuel, yet when used as a fuel cell in a vehicle Honda’s MPG of 6.5 MPG is quite low. The fuel efficiency of BMW’s Hydrogen 7 of 25.2 MPG is only at parity with gasoline.

The efficiency of using solar energy to generate hydrogen may not be the most efficient method. One report from Walt Pyle, Jim Healy, and Reynaldo Cortez Solar Hydrogen Production by Electrolysis indicated that a 1-kilowatt solar photovoltaic device could generate 1 cubic meter of hydrogen in 5.9 hours. Essentially, 5.9 KWHs from a 1KW solar cell produces 1 cubic meter of hydrogen. We know that a pound of hydrogen in liquid state equals approximately 61,000 BTUs (51,500 BTUs at low heat value) or 17.9 KWH.

Research at Caltech, suggests that photoelectrochemistry The Lewis Group may offer a more efficient means of generating hydrogen. We will continue to explore solar efficiency and hydrogen fuel cells to evaluate the economics of alternative energy.

The bottom line is that our dependence on foreign oil is the biggest threat to national security and without cultivation of alternative energies we continue to endure an untenable situation. Further research into solar and hydrogen fuel cells could significantly ameliorate our dependence on oil.

With the Solar Decathlon is taking place in Washington DC today promoting commercially available solar energy technology and oil prices pushing to an all time high of $84/barrel, where are we in terms of cost parity with hydrocarbon fuels. Advances in solar energy technology, lower production costs, and rapidly rising oil costs could bring solar energy into parity with hydrocarbon fuels within five years.

The cost of solar energy remains prohibitively high at about $0.45 per kilowatt-hour (KWH) for an installed system. (a kilowatt-hour equals a 100-watt light in operations for 10 hours and equals 3,412.14 British Thermal Units – BTU) As a reminder, there is significant variance in cost per KWH ($0.23-to-$0.68) because a solar energy system is dependent upon daily available sunlight, which varies from about two hours a day in Alaska to almost six hours in Arizona. Solar energy costs are based on data from solar photovoltaic (PV) supplies SunPower (SPWR) and Sharp Solar.

In comparison to hydrocarbon fuels, one gallon of gasoline has an energy value equal to approximately 125,000 BTUs and cost around $3.00/gallon. The energy value of a gallon of gasoline equates to 36.6 KWH, therefore its price is about $0.08 per KWH. So there is significant disparity between gasoline at $0.08/KWH and solar energy at $0.45.

Fortunately, there are a number of initiatives seeking to improve the economics of solar energy. When we measure the cost of solar energy in dollars per watt we find a complete solar energy systems cost around $8.90/watt. (If we amortize the $8.90/watt over a twenty year expected life of a solar energy system, it amounts to $0.45/KWH) To improve the economic value of solar energy we can lower production costs and/or improve solar efficiency in terms of raising the KWH of electric produced per solar panel.

From the Lewis Group. at Caltech, we learned about several technological approaches to improving solar energy efficiency. Among some of the leading solar technologies are multi-junction semiconductor cells and solar concentrators. In a multi-junction cell, individual cells are made of layers, where each layer captures part of the sunlight passing through the cell. One of the key limits to solar efficiency are the semiconductor band gaps where excess solar energy is lost to heat instead of being converted to electric. Solar concentrators amplify available sunlight and increase the watts per square meter per solar panel.

Last year the Department of Energy reported that solar energy achieved a new record in efficiency performance. The news release, New World Record Achieved in Solar Cell Technology. suggesting that solar concentrators and multi-junction PV cells could surpass the Shockley-Queisser single-junction solar efficiency limit of approximately 31% for single layer solar cell. The multi-junction, concentrator solar cell produced by Boeing-Spectrolab (a Boeing company BA) achieved a world-record conversion efficiency of 40.7% in lab experiments while commercial products operate at 26.5%-to-28.3% efficiency range.

The DOE believes breakthroughs in solar efficiency such as these may lead to systems with an installation cost of only $3 per watt, which translates into a cost of $0.15/KWH. In addition, solar PV cell suppliers are diligently working to reduce production costs. SunPower is targeting a 23% solar efficiency as a goal to reduce its solar energy system cost by 50% by 2012. Semiconductor solar cells benefit from economies of scale, which could reduce cost by 20% for each doubling of production. These solar initiatives should act to reduce solar energy costs.

Meanwhile, as energy costs rise with oil at $84/barrel, the cost of gasoline is expected to increase. If gasoline at the local filling station rises to $6.00/gallon, its cost in KWH jumps to $0.16/KWH. At that price gasoline would be above those achievable through solar energy advancements of $0.15/KWH.

Figure 1 Photovoltaic Device: Efficiency/Cost

With pricing on PV cells falling below $3.00/watt (or $0.15/ kilowatt-hour), solar energy will be close to parity with conventional hydrocarbons. If the cost of gasoline rises to $6.00 a gallon, it would cost $0.16/KWH while current cost of electric is about $0.11/KWH because of the low cost of coal. The bottom line is innovative research initiatives have the potential to deliver disruptive technologies that significantly changes the economics of delivering an energy solutions to all nations.

Further review:
Please see research at California Institute of Technology’s division of Chemical and Chemical Engineering at The Lewis Group.
Imperial College, Jenny Nelson’s Third generation Solar Cells.
DOE’s National Renewable Energy Lab (NREL) Third Generation Solar Photon Conversion (Exceeding the 32% Shockley(Exceeding the 32% Shockley—Queisser Limit)
Solar Energy Market Data Solarbuzz

From our post last week we visited some research at California Institute of Technology’s division of Chemical and Chemical Engineering The Lewis Group and its focus on energy conversion and trade-offs between costs and efficiencies for photovoltaic (PV) devices.

We are providing a brief and very oversimplified analysis of the physics behind solar energy, and to that end, an overview of semiconductor band gaps and new technological approaches to optimize solar energy conversion efficiency. Our prior discussions on energy conversion process, dealt with of the properties of various materials used in silicon and thin-film solar cells. (see Research at Caltech may provide clues to improving solar cell efficiency Energy bands and band gaps provide a way of understanding some of the limitation of solar energy efficiency.

Semiconductor Band Gaps
In semiconductors, the band gap refers to the separation between the valence band, where the electrons are shared among the atoms in the material, and the conduction band where electrons can travel. When the material absorbs light, the electrons, when excited to the band gap threshold level, are able to jump to the conduction band and in the process, create electrons and positively charged holes, that in turn generate electric current.

The energy bands refer to the large number of tightly spaced energy levels associated with crystalline materials. Because electrons behave in wave like movements, their movement interferes with neighboring atoms. The physical properties of semiconductor material are much then those of metals. The minimum energy required to free an electron in metal, ( photo-electric effect) is significantly less than that of semiconductors. For metals the energy bands are more or less continuous, the valence band and the conductive band overlap.

In semiconductor materials such as crystalline, energy bands are grouped into bands, hence energy bands. In crystalline material, the energy bands are split between an upper band called the conductive band and a lower band called the valance band. The energy band gaps in photovoltaic semiconductors are different depending upon materials used. The separations of energy bands in crystalline materials results in gaps between the energy bands and are referred to as the energy band gaps. There are discrete and direct band gap materials. Direct band gap refers to having the conductive band minimum energy value and the maximum valance band energy at the same value such as metals. Please see Bart Van Zeghbroeck’s Principles of Semiconductor Devices chapter 2 for a review of energy bands and semiconductor band gaps.

Figure 1 Semiconductor Band Gaps

With a host of physics equations, models, functions, and laws, one can calculate the energy band gaps for semiconductor materials. In addition, one can alter the band gap of the material through, heat, pressure, or introducing impurities into the material (doping the material) to change its physical properties. In general, the more direct the band gap, the more efficient the band gap material. However, research is working processes to improve efficiencies through doping the material and introducing new materials. The processes seek to narrow the band gap of the semiconductor and thereby improve their efficiencies.

One must remember the cost efficiency tradeoff in evaluating which semiconductor material is best in achieving efficiency and cost parameters. Again, the Shockley-Queisser limit of approximately 30%-to-32% for single junction solar cell and a thermodynamic limit of about 83% are also constraint to improving solar energy efficiency. Please see “Detailed Balance Limit of Efficiency of p-n Junction Solar Cells” (W Shockley and HJ Queisser, Journal of Applied Physics, 1961). Semiconductor materials have limited efficiency because excess photon energy generates heat and not electric current.

Research studies on improving solar energy efficiency are embracing numerous fronts including concentrators and multi-junction semiconductors to impact ionization and spectral conversion. For a quick review, please Imperial College, Jenny Nelson’s Third generation Solar Cells. Multi-junction semiconductors employ two or triple junction semiconductor material to capture excess photon energy. A good overview on solar energy is presented by the DOE’s National Renewable Energy Lab (NREL) Third Generation Solar Photon Conversion (Exceeding the 32% Shockley(Exceeding the 32% Shockley—Queisser Limit)

Figure 2 Approaches to PV Cell Efficiency

There should be considerable excitement given the potential that greater efficiency should be able to drive solar energy costs lower. With PV cells below $3.00/watt (or $0.15/ kilowatt-hour), solar energy with be close to parity with conventional electric rates which are about $0.11/KWH. The bottom line is innovative research has the potential to offer the disruptive technology that significantly changes the economics of delivering an energy solutions to all nations.

With rising energy prices and growing concern over global warming, will advances in solar and alternative energies enable the development of affordable and efficient energy solutions. Caltech research on the energy conversion process may offer some insight.

Energy conversion, ways of converting sunlight to electric and chemical energy, offers promising advancements to make solar and hydrogen energies more practical and affordable. On the forefront of energy conversion research, the framework of developing disruptive energy technologies, is The Lewis Group, that is part of the California Institute of Technology’s division of Chemical and Chemical Engineering. The Lewis Group is working in several research areas some geared towards to better understanding of energy capture, conversion of light into electrical and chemical energy, and energy storage. These research projects include photo-electrochemical, which focuses on the chemistry of semiconductors and materials, surface modification of semiconductors to improve electrical properties, and nanocrystalline titanium dioxide that could potentially lead to significantly lower cost for converting sunlight to electrical energy. The Lewis Group research projects are much more than improving photovoltaic devices; they are also exploring ways to convert sunlight into stored fuel energy.

While we are providing a brief and very oversimplified view of the solar energy research, it is important to understand the dynamics of energy conversion because the conversion process impacts the efficiency and the production cost of photovoltaic (PV) devices and fuels cells. The Lewis Group has an interesting PowerPoint presentation available for download providing an overview of energy from consequences of CO2 emissions to the latest in new technologies to improve alternative energies. Of particular interest are the historical efficiency trends for various materials used in crystalline and thin-film solar cells, energy conversion strategies of turning light to fuel and electric, and the cost/efficiency tradeoff in photovoltaic devices.

Cost/Efficiency Tradeoff
Photovoltaic devices are limited in their practical efficiencies governed by the thermodynamic limits and production costs that involve tradeoffs in materials, production processes, and PV device packaging. The Lewis Group provides a thorough illustration of the efficiency trends for various PV devices materials such as crystalline silicon used in semiconductors as well as the new approaches to thin film PV including amorphous silicon, cadmium telluride (CdTe), copper indium deselenide (CIS) and copper indium gallium deselenide materials (CIGS). These thin film material could offer substantial PV devices price reductions as a result of higher efficiency or lower production costs.

Figure 1 Cost/Efficiency Tradeoff

There is a tradeoff between improving the efficiency of a PV device, that is the amount of electric energy per solar panel, and the cost to produce the PV device. The average efficiency for a PV device is between 15%-to-16% and the average cost between $100-to-$350 a square meter. The cost per square meter and PV efficiency measured in watts per square meter can equate to a cost per watt, which ranges from $1.25/watt to $2.00/watt. SunPower (SPWR), offers the leading PV single junction device efficiency of 22% employing crystalline silicon and is expected to reach 500 megawatts (MW) production capacity by late 2009 from 330 MW in 2007. First Solar (FSLR) is ramping its thin film cadmium telluride (CdTe) solar technology by leveraging its low cost advantage with high volume production with its 75 MW in operations Ohio and 100 MW coming online in Germany. Startup Nanosolar is focusing on thin film solar PVs with a blend of copper indium gallium deselenide (CIGS) materials along with a manufacturing process much like printing, by placing the material blend upon metal foil. Evergreen Solar (ESLR) employs an integrated manufacturing process from wafers to cells and panels based on its proprietary String Ribbon Wafer technology with production levels at 118 MW in 2007.

There is presently a practical limit to solar efficiencies of approximately 30% and a thermodynamic limit of about 83%. The Shockley-Queisser limit at 30% for single junction solar cell efficiency is a function photon absorption in a material. “Detailed Balance Limit of Efficiency of p-n Junction Solar Cells” (W Shockley and HJ Queisser, Journal of Applied Physics, 1961) found that photons delivering excitation energy above a threshold (the band gap) for charge carrier electrons is lost to heating, meaning excess photon energy generates heat and not electric current. Photons with energy levels below the band gap pass through the material and photons above the threshold are absorbed. The absorbed photons transfer their energy to excite the electrons in the material and create pairs of negative electrons and positive charges that, because of their repulsion, travel to opposite ends thereby generating electric current.

According to the Lewis Group, other factors that limit PV cell efficiency include reflective loss of approximately10% for a material like silicon and a fill factor constraint that peaks at 83%. The fill factor restraint is attributable to the current-voltage characteristics of a PV cell that deals with matching the photocurrent density and voltage.

NREL (DOE lab) and Spectrolab (a Boeing company BA) using a multijunction semiconductor approach along with solar concentrators have achieved solar cell efficiencies of 40.7% in lab experiments while commercial products operate at 26.5%-to-28.3% efficiency range. Solar cell suppliers could reduce costs through production improvements or improve PV efficiencies without adding to costs. PV cell suppliers should benefit from economies of scale to reduce production costs while advances in technology improve PV efficiencies.

Research conducted by the Lewis Group at Caltech indicates that materials selected for PV devices have unique properties in their ability to absorb sunlight and generate electricity. In their analysis of semiconductor materials, the Lewis Group research found two parameters, determined by the physical properties of the material, that influence the PV’s efficiency. One is the thickness of the material, measured in microns, required to absorb enough sunlight to bring particular atoms in the material to an excited state, thereby freeing the electron to generate an electric current. The second parameter in the PV material is length of time the excited electrons last before recombining to generate heat instead of electric. Some materials such as silicon require material thickness of 100 microns while gallium arsenide (GaAs) only 1-to-3 microns.

Energy Conversion
Conversion of energy into electric or fuel is advancing through research in photoelectrochemical materials for solid and liquid fuels. Improvements in efficiencies for PV devices and fuel cells offer tremendous potential for transportation and home electric use.

Figure 2 Efficiency of Photovoltaic Devices

From figure 2, it seams quite apparent that PV efficiency has improved substantially since the 1950’s. Please see the Department of Energy (DOE) Basic Research Needs for Solar Energy Utilization for detailed analysis of solar energy. Further progress in PV and fuel cell technologies is predicated upon successful funding of further research. The bottom line is that only through innovative research will a truly disruptive technology be developed that has the ability of changing the economics to deliver an energy solutions to all nations.

Without greater investment into solar and hydrogen energies, we are held hostage to rising oil prices. Alternative energies such as solar and hydrogen fuel cells offer tremendous potential to provide energy independence and energy security. The dependence of the U.S. upon imported foreign oil raises inflation, weakens our currency, exacerbates the trade deficit, and forces consumers to pay higher prices for home heating and transportation. With oil exceeding $80 a barrel in late September 2007, the only beneficiaries are countries exporting oil and oil conglomerates. I guess when countries such as Dubai, after accumulating a large trade surplus based on inflated oil prices, decides to diversify away from oil and buy a non-voting stake in the NASDAQ market, it’s a wake-up call.

To better understand the potential of alternative energy, we should try to understand two basic concepts of energy: Specific Energy and Energy Density. Without digressing into chemistry 101, (Molecular Weight Calculator) the specific energy of a fuel relates the inherent energy of the fuel relative to its weight. Typically, specific energy is measured in kilo-joules (kj) per gram. A joule is a measure of kinetic energy – one joule is the amount of energy needed to move two kilograms at a velocity of one meter per second. Or a kilo-joule equals one kilowatt-second meaning one kilowatt-hour (KWH) equals to 3,600 kilo-joules. Your local electric utility bills you by the KWH, which according to the US Department of Energy Average Retail Price of Electricity in 2007 is approximately $0.11 per KWH.

Table 1 Specific Energy and Energy Density

The specific energy of a fuel tells us how much energy can be derived from a measured amount fuel by weight. By ranking each fuel by its specific energy, one can determine how efficient each fuel is. Specific energy and fuel density are often proportional to the ratio of carbon and hydrogen atoms in the fuel. A reference to the specific energy and energy values of most fuels can be found at Hydrogen Properties

Figure 1 Specific Energy
Figure 1 illustrates how fuels compare according to their specific energy. As we can see, hydrogen, because it’s extremely light, has the highest specific energy in comparison to hydrocarbon fuels.

This however, is not the full story because volume or energy storage requirement becomes a significant factor for gaseous fuels. Specific energy is important to analyze fuel efficiency by weight, but for hydrogen that must be pressurized and cooled to bring to a liquid state, the energy density become more relevant to fuel efficiency.

Figure 2 Energy Density: KWH per Gallon

Figure 2 illustrates how fuels compare according to their energy density, that is, energy relative the container size. As we can see from figure 2, hydrogen, because it is so light, requires 15.9 times the container volume to provide the energy of diesel or oil. In comparison to diesel, ethanol requires 1.6x the container size for the same amount of energy.

The container size becomes a significant detriment for housing hydrogen. Energy density is usually measured in kilo-joules per cubic meter (kj/m3). As kilo-joules are readily translated into KWH by multiplying by the number of seconds in an hour (3,600) and the College of the Deserts’ computation into gallons, we are converting the data into KWH per gallon for those of us in the U.S.

Hydrogen fares poorly relative to energy density. However, technology offers an approach to enhance the benefits of hydrogen with fuel cells. Fuel cell enable hydrogen molecules to interact with oxygen through a membrane that allows transmission in only one direction to convert H2 into an electric current to power your automobile. Fuel Cell Basics Fuel cells often capture the hydrogen electron from hydrocarbon fuel such as methane allow convention fuels to generate hydrogen for electric generation.

In a hydrogen-based economy, solar energy can provide electric to generate hydrogen through electrolysis and vice versa. Jeremy Rifkin’s The Hydrogen Economy eloquently illustrated the hydrogen economy where fuel cell act as mini power plants and the electric network resembles the Internet where cars plug into an electrical grid supplemented by solar cells at your home and work. Electric power generation moves from large utility generation to a distributed generation – everyone plugged in can generate power to the grid. The key benefit of hydrogen is that it democratizes the energy economy bringing power to all countries in the world.

An interesting technical analysis of hydrogen energy is provided by Ulf Bossel and Baldur Eliasson Energy and the Hydrogen Economy The bottom line is that solar and hydrogen energies offer tremendous potential to low long-term fuel costs and improve our environment and climate. More research is required to lower costs and improve feasibility.

There is considerable variance in calculating the cost of solar energy. Using U.S. Solar Radiation Resource Maps from the National Solar Radiation Data BaseThe (NSRDB) we found the amount of kilowatt-hours (KWH) per days of solar radiation per square-meter varies from less than two for Northern Alaska to six KWH/m2 per day for parts of Arizona. Using these maps we found that the cost of solar varies from $0.23-to-$0.68 per KWH with a mean of approximately $0.45 per KWH. The cost of $0.23 per KWH equates to Arizona and $0.68 per KWH reflects the cost of the lower solar radiation in Anchorage, Alaska. These cost are based on data from solar photovoltaic (PV) supplies before tax benefits or rebates. Please see SunPower (SPWR) and Sharp Solar.

Green Econometrics provided a normalized solar energy cost per KWH of $0.38-to-$0.57 with a mean cost of $0.45 as reference for what most of the U.S. would expect for solar energy. We have referred to the Lewis Group at Caltech which has provided estimates of $0.25-to-$0.50 per KWH for the cost of electric production from solar with a mean of $0.38 per KWH. According to Solarbuzz the average price of solar electric is approximately $0.38 per KWH. The Solarbuzz index is based upon an average of 5.5 hours of sunshine per day over a year, which relates to locations such as the US Sunbelt, Latin America, Africa, the Middle East, India and Australia. With large U.S. populations still residing in the North, we would still expect the average home in the U.S. to be paying closer to $0.45 per KWH.

There are a number of factors to consider such as total system cost, the use of concentrators and tracking systems to align the solar panel to be perpendicular with the sun during the day and the property location. There are factors to consider with property location such as whether the roof is facing south or towards the east or west. If the system rests on the ground, shading from building or trees becomes a factor. Other considerations include latitude, climate, weather, and time of day, season, local landscape, and temperature. The Department of Energy provides some information for home owners considering a solar energy system Small Solar Electric Systems

The cost for solar energy systems refers to the average efficiency of solar photovoltaic (PV) panels. The average efficiency for PV devices is between 15%-to-16%. According to SunPower, which has the leading PV device efficiency of 22% there is a practical limit to solar efficiencies of approximately 30%. SunPower is targeting a 23% solar efficiency as a goal to reduce its solar energy system cost by 50% by 2012. Sanyo is second with solar efficiency of 18%. SunPower claims to have patented solar PV architecture and production processes that enable the company to command a lead in solar efficiency.

For solar energy systems below 5 kilowatts, the cost of the inverters represents a substantial part of the system cost. An inverter is used to convert the direct current (DC) from the solar panels to alternating current (AC) used in your home. Inverters can cost from $400-to-$700 per 1000 watt adding to the total cost of deploying small solar energy systems. See Wholesale Solar