Solar thermal technology (ie, solar hot water) provides space heating and/or hot water and is a frequently forgotten member of the solar power family. These highly effective systems are popular in many parts of the globe, from China to Canada to Zimbabwe. The panels are typically 70%-90% efficient, compared to around 20% efficiency for solar photovoltaic (pv) systems. Solar thermal energy displaces the use of the existing hot water heater and heating equipment, typically displacing either natural gas or electricity.
Solar thermal is a more mature technology than solar pv systems that produce electricity. It has been used for centuries for water heating. Even Leonardo Da Vinci had one on his home for heating water.
When considering the installation of such a system, it is important to consider the following items.
In the northern hemisphere, it is best to point the panels facing south. If the mounting surface is not angled to face due south, the efficiency of the system may decrease. If the panels are at a southeast angle for example, performance will improve in the morning, but suffer significantly in the afternoon.
Solar thermal panels are usually mounted in a fixed position and do not have tracking equipment to follow the sun. This is because the panels have copper pipe connected to them and a fluid running through the panel. They also can be heavy and a bit clunky to follow the sun’s angle.
It is important to consider your solar window and how much shade may interfere with the system. Solar thermal panels generate heat, instead of an electric current, so they are not as sensitive to a little shade as pv panels. It is however recommended to have clear solar exposure from 10 am-2 pm as a minimum.
Remember that the sun is lower in the sky in the winter months. If your solar system will provide heat, a good winter solar window is very important. If the roof of your home is not ideal, it is sometimes possible to mount panels as an awning, on the ground, or on a garage.
Space for Solar Equipment
Solar thermal systems in cooler climates require room for a solar storage tank near the existing hot water heater. This heater becomes the back-up when there is not enough sunshine to heat the water. Therefore, you will need space for a tank up to 30 inches in diameter for most applications. It needs to be in a space that will not freeze and will have a pipe connecting it to the existing hot water heater.
If you live in a cooler climate and you have enough room for panels, the solar system can assist with heating your home. Solar works best with forced air furnaces and radiant floor heating systems. Radiators that use boilers operate at a higher temperature and are not usually good for interfacing with solar.
Before forking out a bunch of money on a solar system, it is a good idea to consider energy efficiency first. Weatherization and conservation are often a low hanging fruit for energy and money savings. Water-saving shower heads, front loading washers, and washing clothes with cold water can help to maximize your solar energy.
The sun can heat between 50%-100% of the water used in a home, depending on climate, use, and system size. Efficiency helps increase that percentage, especially on cloudy days.
Sarah Lozanova is the director of marketing for Bubble Train Toys and is passionate about the new green economy. She is a regular contributor to environmental and energy publications and websites, including Natural Home & Garden, Energy International Quarterly, Triple Pundit, Green Business Quarterly, Renewable Energy World, and Green Business Quarterly. Her experience includes work with small-scale solar energy installations and utility-scale wind farms. She earned an MBA in sustainable management from the Presidio Graduate School and is a co-founder of Trees Across the Miles, an urban reforestation initiative.
Photo Credit: Nathan Kipnis Archictects