Solar Hot Water Heating

Solar hot water benefits

One of the most energy intensive (and therefore costly) processes in any house is the heating of water. Heating water accounts for more than 20% of residential energy use in the USA and around 40% of energy used in Australian homes.

This represents not only a massive chunk of your power bill, but also a substantial proportion of carbon dioxide emissions. A solar hot water system, over a period of time, will save you money and lessen your environmental impact.

Solar hot water equipment types

There's two main types of solar hot water systems

Passive: A passive system consists of a tank for hot water storage, a solar collector, piping and frame. The entire system is mounted on the roof. Water heated by the panel flows upward naturally and then is gravity fed into the house.

Active: An electric pump is used to circulate the fluid through the panel collector, meaning that the tank does not need to be on the roof. The advantages of an active system include:

a) can be easier to get local government approval
b) less weight and strain on the roof
c) doesn't require major roof modifications
d) more aesthetically pleasing design

Solar collectors

The solar collector is the business end of a system, heating the water and many advancements have been made in solar collector technology in recent years to improve performance. The most common types of solar collectors:

Flat plate

A flat plate collector is the traditional type and consists of an insulated box containing a black sheet of metal with embedded pipes. The heat is absorbed by the sheet and transferred to the water in the pipes.

Evacuated Tube

An evacuated (or vacuum) tube collector consists of glass tubes with a layer of heat absorbent coating through which water pipes run. As the tubes encasing the water pipes are a vacuum, this reduces heat loss; making them more efficient than flat plate collectors; so these are particularly suited to colder climates. While evacuated tube systems are a little more expensive than flat plate, their increased efficiency (up to 97% thermal energy retention) more than makes up for the added cost.

Heat pumps

Heat pumps are a form of solar hot water technology that don't use any sort of collector. Heat pumps use heat in the air to raise water temperature - even in freezing conditions down to -10 Celsius (14F). A heat pump is like a refrigerator, but in reverse. I've spoken to a few people who have these units, and even in the depths of winter they've had no problems with a steady supply of hot water.