Renewable energy is growing more popular by the day. In the United States, the use of renewable energy grew by 90 percent in the last 20 years, with renewables making up nearly 20 percent of utility-scale U.S. electricity generation in 2020. According to the International Energy Agency, clean energy could account for about 95 percent of the increase in global power capacity between now and 2026.
The reason why renewable energy is seeing this remarkable rise in growth is the many environmental and economic benefits it has. It is often referred to as “clean” energy because it generally produces much fewer greenhouse gas emissions and much less air pollution.
Economically, many forms of renewable energy have reached the point where they are less costly than fossil fuels. According to the International Renewable Energy Agency (IRENA), by 2021, most renewable energy sources were cheaper than the cheaper fossil fuel options.
Currently, homeowners who want to generate their own renewable energy have several options. Depending on location, type of property, and local regulations, options could include small wind energy systems, household hydropower systems, air-source heat pumps (ASHP), or rooftop solar panels. But there are other lesser-known clean energy systems that you may want to consider.
Here are some of them.
1. Solar paint
Solar paint is being developed that would allow you to generate solar energy directly from your exterior walls or rooftop. It would technically work on any large surface that is exposed to sunlight and it could also be used to increase the efficiency of solar panels.
Currently, there are a number of different types of solar paint being developed, including:
- Colloidal quantum dot solar cells: Created by researchers from the University of Toronto, this photovoltaic paint is made of light-absorbing nanoparticles spread over a special film. These nanoparticles —called quantum dots— can produce an electric current thanks to their semiconducting properties. Researchers are still working on increasing its efficiency and lifespan.
- Perovskite solar paint: Perovskite is a light-absorbing and semiconducting material that can turn solar energy into electrical energy, too. In 2014, researchers from the University of Sheffield developed a way to spray liquid perovskite cells on surfaces, to create spray-on solar cells. In the future, this could then be integrated into building surfaces, window glass, rooftops, and other surfaces. Research at MIT in 2019 concluded that incorporating a layer of transparent coating material on top of the solar paint could improve the electrical conductivity of this type of solar paint up to 10 times greater than solar paint alone.
- Hydrogen-collecting solar paint: First developed by the Royal Melbourne Institute of Technology, this solar paint would use a compound called synthetic molybdenum-sulfide, which absorbs water from the air and also acts as a semiconductor, using energy from sunlight to split water atoms into hydrogen and oxygen. The hydrogen would then be used as a source of renewable energy. Mixing this compound with titanium oxide particles could form part of a sun-absorbing, hydrogen-generating paint.
None of these solar paints are being commercially-manufactured yet and they are still not as efficient as silicon-based solar panels, but they are expected to be developed further and could become commercially available in the near future.
In the meantime, painting your rooftop with already-available solar reflective paint can reduce heat build-up in the rooms and areas below, reducing the need for air-conditioning and lowering energy usage. This type of paint is already in wide use on commercial buildings. In 2020, researchers developed a superwhite paint that was so reflective that it can cool a surface below the surrounding air temperature.
2. Solar thermal fuel and home-made water battery
Solar generation has one major constraining factor: solar panels are mainly effective when it is sunny. Cloudy days significantly reduce the efficiency of solar panels — solar panels usually work at 10-25% of their efficiency when the sun is obstructed by clouds.
The solution for this is through storage. Solar energy is usually stored in batteries, which can keep a solar-powered home running at night, or when the weather results in a lowered generation. But this is not a large-scale solution. That is why scientists are looking for other alternatives.
In 2018, Swedish scientists developed a liquid that promises to store solar power for up to 18 years. They developed a liquid “solar thermal fuel” that works like a rechargeable battery, only it uses solar power instead of electric power.
The liquid is pumped through transparent tubes. When it makes contact with sunlight the fuel transforms into an energy-rich isomer, capturing energy in the isomer's chemical bonds. This energy remains trapped even as the molecule cools down. When the liquid then flows through a catalyst, the molecule returns to its original form, releasing the stored energy in the form of heat.
A storage solution more useful for homeowners has been presented by an engineer who runs a YouTube channel called Quint BUILDs. This American DIYer used solar power to pump water up to a tank on his rooftop. He then used the energy of that water to generate an electric current as you can see in the following video.
3. Water pipe turbines for energy recovery
Energy recovery hydropower is a technique that could let you take advantage of the energy of the water flowing through your home’s pipes. It consists of using micro-turbines to turn the water’s pressure into an electric current, with the help of a small generator.
The technique is already being used in some urban water systems to recover some of the energy released, through the use of pressure reduction valves. Precise pressure management is important in water delivery, as too much pressure in pipelines can lead to water loss. Water companies use pressure-reducing valves to regulate flow and water pressure in large, underground lines and ensure water is delivered at the appropriate pressure.
Two separate companies in Oregon have developed and tested systems that use new pressure recovery valves that combine smart pressure control with micro-hydro technologies to generate power from the flow of water through municipal pipes.
Eventually, energy recovery hydropower systems like this could revolutionize micro-hydropower systems for homes by letting homeowners use the water flowing through their pipes to generate renewable energy.
4. Biofuel from food waste
A 2020 study from Penn State showed that U.S. households waste an estimated 30% of the food they purchase. That is a lot of wasted money - and wasted energy. One way to recoup some of these losses is to turn food waste into energy.
While a number of researchers are working on ways to turn food waste into commercial biofuels, according to a science enthusiast from India named Jayanth Sakunaveeti, you can craft a homemade biofuel system for only $2. This man used a water can and PVC pipes to build an airtight container where he could leave food scraps to putrefy.
Food waste contains lipids, phosphates, carbohydrates, etc., and releases natural gases like methane and carbon dioxide as it decomposes. All of this can be converted into bioethanol, biodiesel, and bio-oil.
Biofuel production from food waste is nothing new, but Jayanth Sakunaveeti managed to produce biogas at home by collecting and burning the gases from food decomposition.
One way to reduce your energy footprint is to reduce the size of your home. This is part of the reason for the tiny house trend. The smaller size not only translates into less energy and materials used in construction, but also less energy used to heat, cool, and power a tiny home - saving money as well as reducing carbon emissions.
There are thousands of tiny homes out there, but one modern option is an EcoCapsule. This is something that you can make into an off-grid home, as well as use as a home office, pop-up hotel, glamping, research station - anywhere extra space is needed.
Created by a Slovakian company, the EcoCapsule is a self-sustainable, egg-shaped micro-unit equipped with an 880-watt solar cell array on the rooftop, a 750-watt low-noise wind turbine on a telescopic pole, a passive heat recuperation unit for ventilation and water heating, and a water filtration system that collects rainwater, filters it, and cleans it with a UV LED lamp to make it usable. Additional filters are installed in faucets to provide drinking water.
For solar power storage, the EcoCapsule uses a 9.6-kilowatt-hour battery that lasts approximately 4 days.