What is Solar Water Heating?
I don’t know if you’ve ever had to take a cold shower or bath, but brrrr….! Now I might be giving away my age, but this used to happen a lot before solar hot water gained popularity on the off-grid homestead.
Everything You Need To Know About Solar Hot Water
My Granny Brown didn’t have indoor plumbing until I was around 11. She would draw water from the well and heat it on the stove. We’d then bathe from the dishpan of hot water.
I remember her asking if I had “washed all the importants.” In our family, if we wash off or freshen ourselves from the sink, we say we had a Granny Brown bath.
When I was around 8 or 9 years old, a small pump was put on the well. This meant we could shower outside most of the year without having to draw water for Granny Brown baths. Of course, that’s because we lived in Northeast Louisiana.
When I say shower, I mean a water hose ran from the pump over the top of the well shed and voila! A shower! It was ALWAYS a cold one! So if like me, you want to avoid the cold showers, or you just want to save some money, you may want to find out more about solar water heating options.
Solar Water Heating Basics
Solar water heating utilizes the heat generating power of the sun to heat water. Not surprisingly, solar water heating devices have been used for hundreds of years, but over the last 20 years, absorber technology has come a long way. With these improvements, the solar energy efficiency of collectors can convert more than 50% of the available sunlight for heating water for the home.
Using a solar water heater is one of the most effective ways to increase independence from the failing electrical grid. There’s also the financial savings to consider; the free power of the sun versus the cost of electricity, gas, or oil.
Solar Water Heating Systems and How They Work
Solar water heating systems have two components: the water storage tank and the solar collectors. Also, there are only two types of systems for solar water heating: active and passive. The main difference in these is the active solar water heating system uses a circulating pump with controls while a passive system doesn’t.
Active Solar Water Heating Systems
An active solar water heating system can be either a direct circulation system or an indirect circulation system.
- A direct circulation system has pumps which circulate water through the collectors and back into your home. These work best in climates where freezing temperatures aren’t a problem.
- An Indirect circulation system has pumps which circulate heat transfer fluids through the solar collectors and a heat exchanger. This process transfers heat to the water in the tank. When you need hot water, it’s available. This type of system is best for areas which experience frequent freezing temperatures because the heat transfer fluids don’t freeze.
Passive Solar Water Heating Systems
This type of solar water heating system is usually the least expensive. However, they’re not as efficient as an active system. The passive solar water heating system is usually more reliable and durable than an active solar water heating system.
- An integral collector-storage system works best in climates which rarely experience below freezing temperatures. These systems have a conventional water heater as a backup. If you have a high demand for hot water in the daytime and evening this system will work well for you in such a climate.
- The thermosyphon system works as the water flows through it and the warm water rises as the colder water sinks. The solar collector must be installed below the water tank so warm water will rise into the tank. The tanks on these systems are heavy.
Thermosyphon systems are dependable, but you must have a contractor who knows how to install and construct the necessary forms for the heavy water storage tank. This type of solar water heating system is more expensive and involved than the integral collector-storage system.
About Solar Collectors and Storage Tanks
A well-insulated water storage tank is a must for solar water heating systems. If you want to use solar water heating, you have three types of collectors to choose from.
1 – A flat plate collector
Glazed flat-plate collectors are insulated, weatherproofed boxes containing a dark absorber plate under one or more glass or plastic (polymer) covers. Unglazed flat-plate collectors — typically used for solar pool heating — have a dark absorber plate, made of metal or polymer, without a cover or enclosure – energy.gov
2 – Integral collector-storage (discussed in passive systems)
Also known as ICS or batch systems, feature one or more black tanks or tubes in an insulated, glazed box. Cold water first passes through the solar collector, which preheats the water. The water then continues to a conventional backup water heater, providing a reliable source of hot water. They should be installed only in mild-freeze climates because the outdoor pipes could freeze in severe, cold weather – energy.gov
3 – Evacuated-tube solar collectors
These feature parallel rows of transparent glass tubes. Each tube contains a glass outer tube and inner metal absorber tube attached to a fin. The fin’s coating absorbs solar energy but inhibits radiative heat loss. These collectors are used more frequently for U.S. commercial applications – energy.gov
Many people using solar, wind, or hydropower often have backup systems such as generators. Likewise, a solar water heating system should have a backup for cloudy days. People who use solar power for their homes often have a conventional water heater already installed in line with their solar system. A tankless on demand water heater is an excellent option.
If you live in an area with freezing weather, an outdoor water tank would freeze solid. We have several friends who use solar power for their homes. They all have different setups including woodstove water heaters, but the same basic principles apply.
A few of them have their water heater in line with their solar power supply. When they need hot water, the system kicks in and heats the water in the tank which is hooked to their water storage tank. Another friend has a tankless on-demand system and it works great with their solar power system.
Why Use Solar Hot Water?
- Independence from the power grid: For the same reason people choose to install solar, wind, or hydro systems, people choose to install a solar water heating system. The obvious reason is energy freedom, but the elimination of monthly energy bills is a plus.
- Lessen the impact we have on our environment: Some people call this lightening your footprint. We are all aware of the toxic world we live in.
Financial benefits: According to the U.S. Department of Energy, having a solar power system in place increases the value of the home and land based on the amount of electricity saved over the course of one year. The ratio is, at the current moment, a $20 increase in value for every $1 saved in electric power over an entire year. This could mean a substantial increase in the value of your home and property.
There are tax incentives in place for those who install green energy systems. Check the current state and federal opportunities.
Unless you’re a DIY kind of person or know someone who is good at DIY and would be willing to help you, having a professional install your solar water heating system may be worth the cost.
It’s easy to determine what size tank you need. The solar professionals say you should plan on 15 gallons of hot water per person per day. To me, this number seems excessive, but I guess better safe than a cold shower?
The solar company you choose will have tools to help you determine what size collectors will be needed to heat the amount of water your family needs. They will also help you decide which kind of system and collector will work best in your climate.
Do you have a solar water heating system? We would value your experience and the lessons you’ve learned. Please share your tips with us.
Safe and Happy Journey,
Rhonda and Roxie