Saturday, December 4, 2010

An Introduction to Building a Solar Hot Water Heater

In an increasingly energy-conscious world, renewable sources of electricity are becoming more and more popular. Energy, however, is not limited to electricity: heating and hot water, often provided by oil- or natural gas burning boilers, is another significant contributor to home energy use.
Solar hot water heaters are a method you may consider to deliver clean, hot water to your home.
What is Solar Water Heating, And Why Should I Use It?
Suppose you left a bottle of water out in the sun on a warm, sunny day, and discover that it has warmed to the point of becoming unpleasant to drink when you return to it. In a more common example, you may remember once leaving your car parked in the sun on a Midsummer Day, and finding that the interior of the car has warmed to over one hundred degrees Fahrenheit by the time you got back to it. In either case, you have witnessed solar heating; while direct photovoltaic conversion of solar radiation into electricity is an inefficient process, heating solid matter is a natural effect of sunlight. It is, after all, the Sun's light which raises the temperature of the earth from the ultra-cold temperatures of space by several hundred degrees Fahrenheit (with some help from greenhouse gases), making our home planet livable.
Solar water heaters are engineered to maximize the efficiency, and thus the heat transfer rate, of solar heating. A simple example of how this is done is the classic science project of the solar oven: cover the inside of a semicircle in a reflective material, like aluminum foil, and cover it with a transparent lid. An object placed inside will be heated when the oven is exposed to sunlight. Similar principles are used by solar water heaters to raise the temperature of water to over one hundred degrees Fahrenheit to provide hot water for bathing and other uses.
As long as you receive sufficient sunlight, a solar water heater can work in all seasons, even in cold climates. The materials used to construct a system are simple and inexpensive compared to photovoltaic cells, and there is nothing about building a solar water heater for the home that is as complicated as connecting a home power source to the utility grid.
What Will I Need To Do Before Building A Solar Water Heater?
It is wise to conduct a solar survey to ensure that your home receives enough sunlight to make a solar water heater worthwhile before you do anything else; even if it seems that you receive plenty of sunlight, you may find that obstacles in the path of the sun's light obstruct more sunlight than you thought they could. You will need a sun chart, and a solar elevation and azimuth gage. Using these implements, you will record a chart of the position of the sun throughout the day. If you receive 5-6 hours of unblocked sun centered on solar noon, you should have no problems using a solar water heater.
The calculator at http://www.infinitepower.org/calc_waterheating.htm is a useful tool to help you determine how much money you stand to save by using a solar water heater.
What are The Components of a Solar Water Heater?
The basic elements of solar water heaters include a solar collector, in which incident solar radiation heats the working fluid running through tubing, tubing to connect the parts of the system, and insulated water storage tanks. Since the temperature of your hot water may drop at night once the solar water heater stops working, you will need a backup heater, whether oil burning or electrical.
Inside the solar collector, black painted tubing is run across an insulated box with a reflective bottom and transparent cover. The solar collector is covered by a transparent material to ensure that heat that has entered the collector will not bounce back out, in a manner analogous to the operation of a greenhouse.
What Types Of Solar Water Heaters Are There?
One basic distinction to be made is that between water heaters which use pumps to move the working fluid, and passive systems which rely on convection to move the working fluid. Another is that between open-loop and closed-loop systems; in the former, the working fluid is the water to be heated itself, while in the latter, the working fluid is kept separate from the water to be heated, and transfers heat to the water in the storage tanks by means of a heat exchanger. The use of a closed-loop system allows one to add antifreeze solution to the water in the solar collection loop, so that it will not freeze during the night in cold weather.
What Materials Will I Need?
Materials typically involved in the construction of solar water heaters include:
- Insulated hot water tanks
- copper pipe
- a solar collector
If you intend to build your own homemade solar collector, materials that would be used may include:
- copper pipe
- wooden beams and plywood
- Aluminum flashing
- Kalwall
- Sheet insulation of R value 5 or higher
- Clear silicon caulking
- Aluminum foil and felt paper
- Roofing tar and oil base paint
Solar water heaters can offer many advantages to you if you receive sufficient sunlight. While this guide is only a broad outline by necessity, due to the breadth of the topic, this information will hopefully guide you in the process of building a solar water heater.