With fuel prices rising every year, many people are looking to install more sustainable, and cheaper, energy systems. Although heating technology has not advanced enough to allow us to warm an entire home with solar power, we can now use solar energy to heat our hot water supplies.
In a typical home it is estimated that at least ten percent of the annual energy bill is used on heating hot water, and the other ninety percent on heating rooms. Installing solar powered heating can, therefore, reduce annual heating bills by around $200 a year in homes that are using oil heating systems.
Using solar energy to heat water is still a relatively new concept in America, but it has been used for decades in parts of Europe, including the UK. It is estimated that there are around 200 million solar water heating systems in the world, but only one million systems in the US, which represents around one percent of all households in America.
Who should consider converting?
Using natural gas is a relatively cheap way to heat water, so converting to solar power is really only cost effective for those who are currently running oil heating systems. It is also only cost effective if you use a lot of water. Large families will certainly benefit, but elderly people who are living alone will not save money with solar water heating as their daily usage is so low.
How does solar energy work?
Heating water with solar energy is really very simple. It works in much the same way as a kettle. The solar energy is used to convert solar radiation into electricity, and this electricity is used to heat elements within the water tank to warm up the water.
Solar water heaters, often also called solar domestic hot water systems, comprise two parts, the actual solar collectors and a storage tank. There are different types of solar water heating system, one with a pump, known as an active system, and one which does not have a pump (a passive system).
There are two types of active system. The first type, a direct circulation system, uses a pump to circulate household water through the solar collectors and into the home. This type of system works best in areas where it rarely freezes, so it is not really ideal for New Jersey.
The second, an indirect circulation system, pumps a non-freezing heat transfer fluid through collectors and a heat exchanger. This heats up the water, which then flows into the home. The heat exchanger is essentially like an element inside a kettle. This type of solar heating is better for northern states where freezing temperatures are more common.
Passive solar heating has an advantage over the active type, in that it is cheaper to run and is more reliable. However, they are generally less efficient. There are two types of passive system. The first is an integral collector-storage system. This works well in warmer parts of the country and is also ideal for busy households that use a lot of water during the day and evening.
The second passive system is the thermosyphon system. With these, water flows through the system when warm water rises. The action of heating water creates the cycle. The main disadvantage of these systems is that they have much larger storage tanks which take up a lot of pace in a roof. These tanks are also often heavy, so care must be taken to ensure that they are secured properly on rafters that can adequately support their weight.
How to retain the heat
One problem with using solar energy to heat water is retaining the heat. Unlike conventional hot water heaters, the heating can only take place during the day. There is no option to fire up the furnace to heat the water before taking a bath if you use only solar power, although most systems do allow you to boost the hot water supply with an electric heater.
Care has to be taken to ensure that the hot water supplies are fully insulated so that the heat can be preserved for as long as possible. If you are storing your hot water in the attic space you should insulate this area well, as otherwise the heat will be lost too quickly during the winter months. Few people insulate their roof space in the attic. For this you should use some solid insulation boards. This will, of course, greatly add to the cost of installation.