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In our technologically advanced world, many people believe that they have to spend heavily on tools and equipment and hire professionals to solve complicated problems. While this sounds much easier to do, there are often simpler approaches or solutions that don’t require any of these things. Let’s take solar water heating for example. It is a great solution for people looking to lower their utility bills and reduce their carbon footprint. However, a typical solar water heater available in the market consists of several parts, such as collectors, pipes, temperature probes, and sensors, and costs thousands of dollars to procure and install.
Considering the end product remains the same (hot water), it’s worth asking: Are all these components necessary, especially when considering the high cost of an average heater? Fortunately, it’s entirely possible to build a DIY thermosiphon solar water heater that doesn’t require all the fancy components.
In this post, we’ll explain how solar water heating works, its environmental benefits, and how to build a DIY thermosiphon solar water heater.
Understanding the Dynamics of a Solar Water Heater
Thermosiphon water heating systems rely on the phenomenon of convection in which hotter antifreeze fluids, such as glycol, rise while cooler fluids fall. Hotter fluids are less dense, and as a result, they experience a slightly reduced gravitational pull compared to cooler fluids. This promotes circulation as cold water falls from the storage tank into the collector and hot water from the collector rises back into the storage tank, completing the convective loop.
However, the system requires moderate to high solar radiation to regulate the flow through the pipes. So when the sun stops shining at night, on cloudy days, or during winter, it shuts off effectively. Secondly, the system will function properly if there is sufficient distance between the tank and the collector (usually around 1-2 feet). This head builds the required pressure to ensure unidirectional flow, even at night.
A simple solar water heater consists of two essential components – a storage tank to hold the cold and hot water, and a collector to heat the water. These two components are connected with pipes similar to the assembly of a heat exchanger. Even though the system is generally difficult to build on your own, it’s still doable as long as you thoroughly follow the instructions. Plus, you can manage without the additional components, such as thermostats, controllers, and other sensors. Many people build a DIY thermosiphon solar water heater using mostly repurposed materials like old geysers, plastic bottles, and frames built from scrap metal. This way, they can avoid spending thousands of dollars and build a heater in a few hundred dollars.
Benefits of Solar Water Heating
A solar water heater uses solar radiation to heat water for several purposes. You can use it to heat water in your home, your pool, or even a Jacuzzi. Many residential and commercial buildings have installed large-scale solar heaters to reduce their overall costs and tap into the sun’s unlimited energy source. The following are the main benefits of investing in solar water heating:
Solar water heating systems generally require a heavy one-time investment. However, they pay for themselves in the long run by reducing or eliminating escalating costs of electricity, gas, or oil. Plus, federal and state governments are increasingly offering great financial incentives for going solar through tax credits. If the only reason you haven’t gone solar yet is the high upfront cost, you can learn how to build a DIY thermosiphon solar water heater and save thousands of dollars in procurement and professional installation costs. So as long as you live in an area with moderate to high sunshine and high utility costs, you have the opportunity to kill two birds with one stone by solving your water heating and billing problem.
2. Eco-Friendly Solution
Most heating systems that use gas or oil involve burning fossil fuels directly to heat water. Conventional electrical heating systems use electricity generated from fossil fuel, coal, or hydroelectric power plants that carry a massive carbon footprint. As a result, they increase pollution and add to our environment and health problems, such as poor air quality, eco-system disruption, global climate change, smog, respiratory diseases, cancer, etc. Scientists now understand the severe consequences of using fossil fuels to generate energy which is why they are supporting every emerging sustainable energy resource. By using a solar water heater, you can reduce your carbon footprint and play your role in saving the environment by minimizing or eliminating gas, electricity, or oil usage to heat water.
According to several sources, energy consumption will only rise in the future and increase the depletion rate of our finite energy sources, such as fossil fuels and gas. As a consequence, future generations may not have access to energy sources we take for granted every day. Solar water heating is not only a sustainable solution but also one of the few solutions that can help stretch finite energy sources beyond their expected lifespan. A residential solar water heater can reduce your water heating bill by 50-80%, and you can save even more money by opting for the DIY route. Now imagine if a hundred or a thousand homeowners do the same. It could initiate a domino effect that can reverse some of the environmental and economic impacts of fossil fuels.
The performance of your solar water heating system depends on your geographical location and climate conditions. The higher the intensity of solar radiation, the more effective and efficient your system is. For instance, states such as Arizona, New Mexico, California, and Nevada have longer sunlight hours and hence, are better suited for thermosiphon solar water heaters. In contrast, northern states, like Washington, New York, Colorado, and Illinois, have a colder, wetter climate due to rainfall, overcast conditions, and snowfall. Regardless, these systems are still effective in winter or wet conditions since they employ radiator fluid technology that supports the heat exchange during this time.
Shortcomings of DIY Solar Water Heaters
Even though solar water heating is a highly reliable and sustainable solution, it does come with a few minor drawbacks, such as:
1. Freezing or Overheating Due to Poor Design
If you’re looking to build a DIY thermosiphon solar water heater, you need to select the build material properly according to the weather conditions. A poorly designed or installed system can easily malfunction by overheating or freezing and become a safety hazard.
2. Availability of Parts
Depending on where you live, you might not find high-quality parts, professional guidance, or installation services. This is why many homeowners opt for the DIY route and have to manage with inefficient systems or high costs.
3. Inconsistent Reliability
As mentioned earlier, the efficiency of a DIY solar heater depends on several conditions, including the design, built materials, and weather conditions. As a result, the reliability of the system varies in general. For example, two heaters with the same design and materials can have different efficiency ratings in different locations. Furthermore, if your home’s water supply is hard or acidic, it could corrode your circulation systems and storage tank quickly, leading to high maintenance or replacement costs.
4. Building Orientation and Regulations
To build an efficient system, you’ll need to ensure that your residence has sufficient sunlight exposure. This is generally not possible in city dwellings with large buildings nearby. Secondly, many areas, especially those prone to hurricanes and earthquakes generally have low weight limits for roof-mounted equipment so you might not be allowed to install a DIY solar water heater.
How to Build a DIY Thermosiphon Solar Water Heater
Building a DIY solar water heater is considered the simplest system to install at home but isn’t necessarily a piece of cake. You need the proper tools, equipment, materials, and a solid design to ensure it functions well. If you actively spend time in your backyard or garage building things or have experience in home maintenance and basic workshop, you shouldn’t have a problem installing a few pipes, fitting glass, and attaching it to a storage tank.
Here’s a brief overview of the design process:
- An insulated storage tank (You can use an old electric water heater tank as long as it is in good shape).
- Black paint for maximum absorption
- Glass sheets
- Aluminum sheets
- Insulation material
1. Building the Solar Collector
First, you’ll need to make an insulated frame using plywood and add a roll of aluminum to the front to absorb sunlight and heat efficiently. To ensure the sunlight doesn’t reflect, you can paint the aluminum sheet black as well. Next, you need to install the pipes. We recommend using copper pipes to form the grid with an inlet and outlet. Finally, you need to assemble the structure by fitting a glass sheet on top and attaching everything with bolts and screws. Your solar collector is now ready to be connected to the storage tank. You can mount it on the roof or the side of your house, whichever is more convenient.
2. Storage Tank
A storage tank typically contains two partitions – one for cold water and the other for hot water with inlet and outlet drains on both sides. You need to route the cold water to the cold water inlet and the outgoing hot water to the outlet. And there you have it – A DIY thermosiphon solar water heater.
If you are determined to build it yourself, here’s a full video about the process:
Frequently Asked Questions
The following are some frequently asked questions about solar water heating:
1. What is the Thermosiphon effect?
The thermosiphon effect describes the passive heat exchange between fluids in a system through convection which results in natural circulation of the fluid without a mechanical pump. Thermosiphons are commonly used in heating applications, such as water solar heaters, furnaces, and boilers.
2. Does a Thermosiphon heater need electricity?
No, a thermosiphon heater does not require electricity to function as it heats water through convection and circulates it to the storage tank without a mechanical pump.
3. Does a solar heater function in winter?
Solar heaters can work in winter. However, their efficiency and effectiveness depend on several factors, such as the design, insulation, build material, and collector fluid. For instance, most homeowners switch to antifreeze (glycol) during winter to prevent the fluids from freezing.
4. Does the solar water heater work at night?
As their name suggests, these heaters need solar radiation to work so they cannot function at night. However, they can still provide hot water for up to 12 hours, depending on your location, as long as you insulate the storage tank and pipes properly.
5. How do I keep my solar water heater from freezing?
The best way to keep your solar water heater from freezing during winter is to use an antifreeze fluid instead of water. This will also protect your solar collector from damage as the water expands upon freezing.
6. Do solar water heaters function properly in overcast conditions?
Yes, solar water heaters work on cloudy days as well as long as there is sufficient solar radiation to heat the fluid and promote heat transfer and circulation into the storage tank.
7. How effective is a solar water heater?
Solar water heaters are highly efficient and capable of turning nearly 80% of the absorbed solar radiation into thermal energy required to produce heated water in the collector.
A DIY thermosiphon solar water heater is an ideal solution to reduce your energy bill. Plus, you don’t have to invest in an expensive system to reap its benefits. By opting for the DIY route, you can build a working system in just a few hundred dollars. However, to ensure your system is efficient, you need to consider several factors, such as your location, water requirement, annual utility costs, heat loss, and sunlight hours. This will help you design your system accordingly in terms of storage capacity, head, mounting, surface area, etc.
If you think this is too much work or cannot find the time to invest in this project, you can always shell out the cash for a commercially available solar water heater and professional installation services. Whichever option you choose, you’ll be saving money in the long run by turning solar heat into warm water.
You can find plenty of choices online, such as this one on Amazon, which I believe is a good quality product:
Thermosiphon solar heaters, do not generate electricity like solar panels (we wrote about how much you can save with those, here), they use the solar radiation directly to heat up water. Similar techology is used with solar pool covers, where the pool water is heated up by sunlight also saving a lot of energy.