HOW SOLAR THERMAL PANELS WORK

Solar Thermal

Over the coming weeks I’ll be discussing a number of renewable energy technologies that can be applied to your home or business in order to save on energy costs and reduce the carbon footprint of your building. The topic for next two weeks will be solar power. When most people think of solar power they think of photovoltaic panels that turn energy from the sun directly into electricity. We’ll be going over that next week. What we’re looking at today is solar thermal energy.
What is Solar Thermal Energy?
Solar thermal energy refers to the process of using the sun’s energy to heat something up. The heat can be used to provide hot water for residential or commercial use, space heating using radiant floors or panels, or converted to electrical power via a turbine. The focus of this entry will be solar thermal for hot water and space heating because these topics are of the most interest to a building owner looking to incorporate some renewable energy.
What goes into a solar hot water system?
A solar hot water system uses a solar collector that heats a fluid which is either used directly (if the fluid is water) or is used in a heat exchanger to heat water. Water can generally only be used in warm climates where freezing is not a worry. In these situations a flat plate collector is used. The flat plate collector is basically an insulated box with a clear glass or plastic top that has a dark colored copper or aluminum absorber plate connected to a series of pipes that water flows through. The sun heats up the absorber plate which heats up the water pipes and the water itself, while the box prevents heat from escaping to the environment. A flat plate system with water as the fluid can be used to heat a pool or to provide domestic hot water for the home.
In cooler climates a solar thermal system can still be very effective, but a different fluid is needed to prevent freezing. Generally a mixture of glycol and water is used. This fluid can be used in flat plate collectors, or evacuated tube collectors. Evacuated tube collectors have one larger tube with a smaller tube inside of it in which there is a fluid. The space between the tubes is vacuum-sealed to provide near-perfect insulation, so the radiant energy heats the fluid and the heat cannot escape. The heated fluid rises to a manifold at the top of the tubes through which the glycol mixture is being pumped. The heat from the fluid inside the tubes is transferred to the glycol mixture. The glycol then goes through another heat exchanger that heats pure water.
The water that is heated can be used directly for domestic or commercial use, or it can be used to heat your home using radiant floor heating, radiant panels, or a forced air system. Regardless of the use, a system usually incorporates a pump, one or more heat exchangers, and a tank to store hot water. Specification of the components and layout of the system should be performed by a qualified Mechanical, Electrical, and Plumbing Engineer.

Images courtesy of the U.S. DOE: http://www1.eere.energy.gov/solar/sh_basics_collectors.html
How long will it take to pay for itself?
Generally solar thermal collectors are cheaper to buy and install than photovoltaic panels, but a detailed technical and economical analysis is needed to determine how long it will take for energy savings to exceed installation costs. Some things to take into account are:
· The solar resources available which depends on latitude, local climate, cloud cover, and shading.
· The efficiency of the solar collector which depends on the collector itself, the fluid to be used, orientation, and placement.
· Cost of equipment purchase and installation.
· Incentives that may be available through federal, state, and local governments as well as utility companies.

Energy 1 is a company that can provide a feasibility study that takes all of this into account and provides you with the information you need to know like savings on your monthly energy costs, payback period, installation costs, etc. They can also provide feasibility studies for photovoltaics, wind energy, micro-hydro, cogeneration, and geothermal energy.
If you aren’t concerned with detailed economic analysis and would like to “jump right in” you should still be aware of the incentives available to offset the cost of your project. Energy 1 can give you a comprehensive break down on Federal, State and Local tax grants and incentives. In most cases this can give a residential application a payback in less than 7 years.

How can I get a Solar Hot Water system for my building?
Need a hand installing your system? For an easy no-headache installation Energy 1 can do a feasibility study, provide the design, install the system, and provide routine maintenance on your installed system. Or call (406) 587-2917.