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The Power of the Sun from Eco-Logic Blog (USA)

Credits: ©2009 Eco-Logic/Robin Rogers

According to the U.S. Energy Information Administration, 76 percent of all power-plant-generated electricity is used to operate buildings, and half of U.S. energy production is from coal. The U.S. Environmental Protection Agency estimates carbon-dioxide emissions from the U.S. electric-power sector are equal to 40 percent of all CO2 emissions in the U.S. Compared to coal, oil, natural gas and mined uranium combined, the amount of solar energy reaching the surface of the planet in one year is about twice as much as will ever be obtained from those non-renewable resources. And the sun is highly unlikely to extinguish--at least not for another five-billion-plus years (I’ve heard)--and it provides a cleaner, viable alternative to fossil fuels. Using solar energy to power our buildings is gaining in popularity. The Solar Energy Industries Association estimates from 2006-07, new solar installations increased by more than 40 percent. According to “Clean Energy Trends 2009” by Clean Edge, the photovoltaic industry had 190,000 jobs in 2009.

 

Desert Solar Farm

In January 2009, while almost all industries and types of real estate were suffering in the U.S., applications to build solar projects in areas managed by the Bureau of Land Management were up by 78%. The projects were all ten megawatts or greater solar power plants. The ideal real estate for these mega solar farms is desert land in California, Nevada, Utah, Colorado, Arizona and New Mexico. In January there were a total of 223 applications submitted for approval and seeking a combined acreage of 2.3 million. ©2009 Jake Gosselin

The Power of Incentives
Municipalities, states and the federal government can encourage solar with direct incentive programs, such as tax credits, depreciation allowances and liability shields, just as they do for fossil fuels. An increasingly favored option is to set up Renewable Portfolio Standards, such as those adopted in Colorado, whereby utilities must purchase a certain percentage of solar or renewable energy. Also known as Feed-in Tariffs, or FiTs, they are basically payments per kilowatt hour for electricity generated by a renewable resource. The World Future Council reports it has been empirically proven that FiTs are the world's most successful policy mechanism for stimulating the rapid development of renewable energy.

Gainesville, Fla., became the first U.S. city to adopt FiTs last spring. Residents there with photovoltaic panels on their roofs will receive 32 cents per kilowatt hour versus paying about 12 cents per kWh for their electricity, according to U.S. Department of Energy statistics. In Canada, an innovative FiT scheme awards higher incentives for small rooftop solar installations than for off-shore wind.

San Francisco’s approach was to provide incentives directly to residents and businesses for installing solar power on their properties. The GoSolarSF program prompted a 450 percent increase in applications for solar installations during the first year. It is also deploying large-scale commercial solar incentives that phase out over time as costs go down for solar.

Berkeley, Calif.’s municipal-tax-assessment rebate program is soon to be adopted at the federal level, promoted by Vice President Joe Biden. At the state level, California features a monetary incentive based on actual performance during the first five years for large-scale PV systems and a one-time, up-front payment based on estimated performance for systems of less than 50kW.

Much of the increase in U.S. solar installations has been on individual buildings, generating power that is then fed into the existing power grid. Called net metering, it is now offered in 42 states, some of which offer incentives for installing such power systems. To see what’s available in your state, see the up-to-date DSIRE Solar database that tracks all rebates, tax credits and incentives across the U.S.

To further grow the U.S. solar industry, Mark Z. Jacobson of Stanford University and Mark A. Delucchi of MIT have proposed combining FiTs with a declining clock or reverse auction, such as was proposed in California last August. In this type of scheme, the right to sell power to the grid goes to the lowest bidder. For example, a solar developer would bid on providing power to one of California’s utilities; if it had the lowest bid, the utility would award a power-purchase agreement, effectively eliminating risk for the developer by guaranteeing a market and simultaneously allowing the market to set electricity rates for PV projects in California up to 20 megawatts. The authors write that these reverse auctions could provide an ongoing incentive for renewable-energy developers to lower costs, eventually phasing out FiTs.

Storing Solar Energy
What happens to the grid when there’s a cloudy day? For large-scale solar power, how is the energy stored for use when the sun is not shining? And how can it be transmitted across long distances?

DOE handed out almost $12 million last summer to five projects, looking at solar-energy-grid integration and big-capacity storage. Solutions might include compressed air storage or pumped hydro where water is pumped up to a reservoir and then released later—often during peak demand-- through turbines to generate electricity. SolarReserve of California is applying to build a 150-megawatt solar farm that will store seven hours’ worth of the sun’s energy in molten salt. Heat from the salt can be released when it’s cloudy or at night to create steam that drives an electricity-generating turbine.

Implementing Solar
So where to begin?

For new construction, first design to capture passive opportunities that require no mechanical or electrical components, thereby reducing or eliminating the need for mechanical cooling and heating, as well as daytime electric lighting. Three primary areas--climate, heat transfer of building materials and human thermal comfort--are addressed using site and location, building orientation, prevailing climate, glazing and shading, and thermal massing for all passive-design decisions.

The general goal is to make the building as energy efficient as possible before incorporating solar electricity, and strategies will vary depending on the location. This will usually help maximize most other elements and can reduce size requirements of necessary systems, such as PV or heating and cooling. Perform energy modeling with a program, such as DOE-2, that allows custom weighting to get an accurate snapshot of direct-gain and natural ventilation using passive strategies. Also make sure your building design allows active solar with roof, walls or site area situated to accept PV whether as building-integrated systems or attached arrays.

The recently completed Omega Center for Sustainable Living provides an example where the design team used DOE-2's eQUEST to model estimated energy use. Located in New York, the building supplies all its own energy needs and operates carbon neutral. The self-sustaining structure is heated and cooled using geothermal systems and utilizes PV power.

Retrofit of existing buildings is also feasible by incorporating improved insulation and high-performance triple-glazed windows, reducing thermal bridges, sealing air leaks, adding a ventilation system with highly efficient heat recovery, relying on solar hot water and highly efficient condensing gas boilers, as well as integrating solar thermal with existing, conventional heating systems.

If you’re not already following your building’s energy use with Energy Star’s Portfolio Manager, you may want to check it out to help you track and assess energy and water usage in your buildings. Last August, the program was updated so on-site power from solar or wind can be included in the fuel mix.

Benefits
At the risk of stating the obvious, solar energy is free once you’ve constructed a building according to passive design principles or a system with active panels, immediately avoiding the cost of fuel. If a grid-tied project is generating more electricity than the building’s energy requirements, there’s the potential to earn money and there are no battery disposal issues. So far, there’s also no fuel tax on solar energy, so the building owner avoids paying some taxes on this virtually unlimited resource. Incentives are closing the gap between purchase and pay-back. Active systems are usually low-maintenance and often carry at least a 20-year warranty on modules.

Solar power is inherently flexible, as it can be implemented in so many ways--building integrated PV, solar hot-water collectors, site- or building-mounted arrays, integrated systems that can also provide shading, thermal masses, trombe walls, special glazing, scalable systems, etc. As a building’s energy requirements are reduced, other negative aspects, such as air and water pollution and ozone depletion, that result from combusting fossil fuels are also decreased. Finally, with small- or large-scale solar-energy systems, there is greater energy independence, which can contribute positively to national security. So, check out the resources below and get started!