Solar Cogeneration: Highest Utilization of the Sun's Resources

Renewable heat & electricity in one
Over the last decade, technology advancements coupled with rebates and incentives have made “going green” not only an environmentally responsible choice, but also a strategic, cost-saving business move. However, while renewable energy can be an effective solution to meet sustainability objectives and improve the bottom line, selecting the right technology can be an exhausting process.

The two fundamental solar technologies, solar photovoltaic (PV) and solar thermal, are valuable energy resources. So, why choose between the two? With solar cogeneration, a need for electricity and hot water are met in a single array. The dual production of energy in both forms results in payback times that are typically one-half that of standalone PV or solar hot water systems.

How it works
Solar cogeneration combines proven PV and solar thermal technologies to maximize total collected energy and optimize economic benefits for institutional, commercial, and industrial customers. Using up to 75% of the sun’s delivered energy, a cogeneration solution captures excess heat that standard PV panels dissipate as waste and transfers the heat away from the solar collector to produce useful, hot water. 

This technology improves upon pure PV systems, which are still only 15% to 20% efficient and waste nearly 80% of the sun’s usable energy. Cogeneration technology, in contrast, uses up to 75% of the delivered energy with the added benefit of cooling the solar cells in the process—thereby, improving cell efficiency, which otherwise drops with elevated temperatures. By transferring heat away from the PV cells to produce hot water, solar cogeneration increases electricity output, while extending the output and lifespan of a system.

Where it works
Solar cogeneration technology addresses an existing, but underserved market: industrial, commercial, and institutional facilities that use hot water for a variety of applications. According to 2007 data from the Department of Energy’s Energy Information Administration (EIA), the United States consumes 315 billion therms per year in heat usage (commercial customers typically pay around $.75 to $1.20 per therm—an enormous expenditure). Solar cogeneration can economically reach applicable temperatures to address between 30% and 50% of the nation’s thermal energy needs.

Facilities that fall into this market include energy intensive industrial sites that process food, beverages, textiles, paper and pharmaceuticals, among others, as well as institutional sites that house communities of people such as dormitories, military bases, multi-tenant housing complexes, hotels/resorts, and hospitals. The electricity generated is fed directly to a building’s existing power supply, while hot water is used for a range of applications, such as washing and amenities, pasteurization, as well as fermentation and boiler pre-heating, to name a few.

The future of solar
The current global commercial and industrial solar hot water market is estimated at more than $18 billion USD and is expected to continue to grow, exceeding 25% growth per year to nearly $30 billion USD during 2012 and 2013.

Reducing operating costs, today and into the future, is a major goal. Solar cogeneration solutions result in natural gas (or LPG) and electricity savings, while helping businesses achieve sustainable supply-chain and greenhouse gas reduction goals. Implementing renewable energy solutions also helps customers achieve LEED qualification points and Energy Star ratings.

Another important driver is government mandates for renewables. For example, the 2005 Energy Policy Act requires existing and new federal facilities—prisons, military bases, public hospitals, etc.—to offset 30% of the energy used to heat water with solar thermal where economically feasible. Other solar thermal incentive programs include NYSERDA, California Solar Initiative (CSI), and REC and tax credits in Arizona, North Carolina, and Hawaii. Solar cogeneration technology is uniquely eligible for solar electric and thermal state incentives, in addition to federal programs, such as the Section 1603 treasury grant/investment tax credit (ITC) and accelerated depreciation, offered for renewable energy projects. 

Upfront costs can be considerable, but are no longer a hurdle to adoption. With the recent availability of PPA (Power Purchase Agreement) financing models specific to cogeneration, called HPPAs, or Heat & Power Purchase Agreements, industrial, institutional, and commercial customers can benefit from a dual-power generation solution from day one, locking in fares below utility rates.

Solar cogeneration technology for commercial and industrial applications is a relatively new development, evolving from primitive solar hot water collectors, dating back to before 1900, and comprised of a black-painted tank mounted on a roof. Separately, both traditional solar technologies have been refined and commercialized, so that today customers can benefit by generating electricity and hot water in the same solar architecture—combining existing technologies and mature supply chains. The solar electric and thermal elements form a symbiotic relationship, working in tandem to improve overall system performance and increase energy output at a low cost per energy produced.


Dr Gilad Almogy is the CEO of Cogenra Solar.

Cogenra Solar
www.cogenra.com