Parabolic Trough: Hot Water & PV Electricity Production in One System

published: 2011-09-21 8:41 | editor: | category: Knowledge

A private home in the prestigious Martha's Vineyard, Massachusetts may have the first known installation of a thermal parabolic concentrator for a residential property in the United States. Typically, homeowners who desire hot water provided from a solar energy system could choose between an evacuated tube and a flat plate collector.

The property owner, Paul Adler received a grant from the Massachusetts Clean Energy Center (MassCEC). Mr. Adler, who has designed and built passive solar homes for nearly 40 years, states he has studied “solar thermal and solar electric for years” and continuously searched for a system capable of providing space heat and electricity.

He received the grant as part of a MassCEC's $1 million pilot program for 60 homeowners to install solar thermal technology in their homes. MassCEC, the state agency in charge of Massachusetts's renewable energy initiatives, wants to determine how solar thermal works as an “energy saver.”

Privately held SolarTron Energy Systems Inc., a company out of Nova, Scotia, Canada owns and manufacturers  the patented system, called SolarBeam, as “the world's first affordable system for solar hot water & photovoltaic electricity production.”

The company CEO, Edward Herniak states on the company's website, “The SolarBeam is 262% more efficient that hot water panels and 98% more efficient than evacuated tube technology when used in process heat applications.” He expects the system to generate 3.5 kilowatt of electricity per kilowatt-hour sometime in 2012.

The System

SolarBeam uses a concentrator that collects sunlight directly onto a 15-foot diameter dish. A 10-by-10 collector “absorbs” the sun's rays and direct the energy onto copper coils, which have that has water running through them. On a sunny day, the absorber can reach temperatures as high as 1200 degrees Fahrenheit. A series of insulated pipes distributes the thermal energy to the home. The water provides hot water, space heating or air condition through a process called absorption chilling.

SolarBeam emphasizes a less complicated system that features a parabolic trough installed on top of an eight-foot pedestal, within 150 feet of the house. The ideal site lies about 20 feet from the building and faces south. The site must be free of trees or other obstructions, which shade the equipment.

Some designs may require a rooftop mounting system where trees may obstruct the trough's   direct exposure to the rays of the sun. The SolarBeam system has a two-axis tracking mechanism that allows movement of trough in two directions. The tracking device includes a GPS navigational system found in expensive telescopes.

SolarTron claims the energy output of a single parabolic trough, 10 kWh has the energy output of 15 average flat plate thermal connectors and 25 photovoltaic modules. Compared to the 900 square feet of surface area required for the installation of collectors and PV panels, SolarBeam needs only 250 square feet to reach the same output level.

Flat plate collectors have a high heat loss during the winter months. This occurs because of the high amount of glass and copper tubing radiating heat to the cold temperature. The effect is not as great for SolarBeam. It does not overheat or experience the stagnation typical of flat plate technology. Stagnation occurs when the collector absorbs heat, but the application has all the heat it can handle. As a result, the collector becomes damaged or presents a potential hazard. SolarBeam automatically pivots away from the sun until it has a need to absorb more sunlight.

Payback

Currently, the cost of a single SolarBeam system runs an average of $27, 500 per unit - delivered and installed. The system's cost, before applying rebates, incentives or tax credits, and energy output makes, it a more economical choice for large homes with hot water, space heating and a swimming pool. The available state and federal incentives reduce the cost of SolarBeam 30 to 40 percent.

SolarTron claims the system pays for itself in 3 to 8 years. The payback period depends on the cost of electricity, gas or other fuel, the average daily sunlight system design and the needs of the home. Adler recommends homeowners with an average size home install standard evacuated tube of flat plate systems to provide hot water. It is also suitable for commercial applications.

Conclusion

The SolarBeam structure and reflective surfaces have ten-year warranties. The drive train system carries a three-year guarantee. Owners can purchase additional warranty coverage for $300 annually.

Adler, who also installed the system,sees such great potential for the system that he formed Southern New England Solar, LLC andsecured distributorship rights for the technology in Massachusetts, Connecticut, and Rhode Island. The SolarBeam technology has a registration and certification by the independent testing lab Solar Rating and Certification Corporation (SRCC) - a requirement for receiving federal or state funds for installed solar equipment.

Within the next few months, Solartron will ship to Mr. Adler high temperature PV solar cells designed for insertion into the unit's absorber. The triple junction PV solar cells enable the system to generate up to 4.4 kWh of electricity and 8 kWh of hot water at the same time. When this occurs, SolarBeam becomes the first solar collector on the market with technology to generate electricity and thermal energy simultaneously.

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