Alternative Ways to Incorporate Solar into Your Dwelling

There’s more to Solar Energy than Rooftop Panels: Alternative Ways to Incorporate Solar into Your Dwelling

By Ellen Rubin

People have been embracing solar panels to make their homes more sustainable. Including those that subscribe or have bought into community solar programs, over 27.5 million homes in the US are taking advantage of solar energy to help reduce their reliance on, and expense of, utility companies. This number is projected to increase to 65 million homes by 2028.

Relying on fossil fuels alone leads to greater climate change; and climate change has made our weather less predictable and more extreme. Major heat events stress power grids and heavy storms lead to disrupted service. Having an independent source of energy helps in these instances, and solar power can be the most accessible for many people.

If your goal is to become more self-reliant, reduce your environmental footprint, or just reduce your utility bill, and you want to use solar power, not everyone can add solar panels to their roofs. Apartment dwellers and renters don’t own their homes and may not have access to, or permission, to use rooftop space to add panels.

82% of new homes are part of Home Owner Associations (HOAs) that may restrict what residents can do, even if you live in a free-standing home. Issues such as local ordinances, very large shade trees, and the structural integrity, shape, or orientation of the roof can impact the economic and practical feasibility of using solar panels.

Don’t lose heart, there are still ways in which you can incorporate solar technologies into your home, and there are new technologies being investigated that are potentially impactful once they become commercially available. New solar breakthroughs are being announced almost on a daily basis.

Quick Overview of Traditional Panels

A casual understanding of how traditional panels work and their advantages may help in understanding newer technologies. Most obviously, photovoltaic solar panels (PV) use sunlight to create electricity. Current versions can use a broader spectrum of light than the original PV panels, yet they don’t take advantage of ultraviolet or infrared waves. Experimentation is being done to use thermoelectric generators to exploit the temperature differences that occur between night and day so that panels can become a 24-hour renewable energy source. Scientists in China are experimenting with a triboelectric nanogenerator that harnesses the kinetic energy of raindrops to produce energy. However, if you purchase panels, you will probably only find the basic photovoltaic panels that are able to convert up to 25% of the sun’s light to electricity. This is known as its efficiency rating. Panels generally last a minimum of 20 years.

PV panels are usually mounted to frames that are bolted or anchored to the rafters of the roof through the shingles. The angle and directionality of the roof will dictate how much energy the panel can potentially create. They need to stay clean, and clouds, shade, and heavy layers of snow will reduce or negate this potential.

There are a number of reasons why solar panels would not be an owners’ first choice:

• The HOA has covenants against solar panels.
• They can be obtrusive looking. Some people just want to preserve the integrity of their home’s aesthetics, especially if it’s a historic structure.
• The roof has an unusual shape and won’t accommodate sufficient panels to make the wiring worthwhile.
• Some types of roofing don’t easily lend themselves to using panels. For instance, you need special products and specialized knowledge to put panels on a slate, metal, or ceramic tile roof. The tiles may have to be lifted to secure the panel, then replaced. Wooden roofs may not be sturdy enough to support panels, and panels on flat roofs require angled bracing.
• Certain climates make solar panels much less efficient. They work best in clear, sunny skies and cool to cold weather.

It’s impractical to assume that skyscrapers and multi-unit buildings will have enough roof space to power the entire building. This doesn’t mean that it isn’t worthwhile, just that other sources are needed to supplement power requirements. Some of the newer innovations, such as solar windows or vertical and integral façade installations address this issue. Solar technology is increasing at a rapid rate, so newer materials that create lighter, more flexible, more efficient solar receptors, and are more ecologically sustainable and less expensive to produce will lead to the creation of additional building materials that will help make us less reliant on fossil fuel energy sources.

Finally, if you rent, you may not have the ability to install panels on your roof. If you are committed to including solar to reduce your carbon footprint, you may be able to use some of the options described below.

Alternative Ways to Incorporate Solar Power

Solar Shingles

If you are dealing with an awkwardly shaped roof, multiple chimneys, or HOA rules prohibiting panels, yet still want to go solar, don’t worry, solar technology has advanced so that the shingles themselves are solar panels. First introduced in the 2005, solar shingles have been improving and gaining in popularity, first in Europe, and now around the world. They can mimic traditional asphalt shingles, slate, or ceramic tiles while retaining the clean roof lines and aesthetics of traditional roofing materials.

Solar shingles are less bulky than conventional solar panels. Originally, they weren’t nearly as efficient as panels, but that gap is quickly closing. Shingles can be made from either:

• Copper indium gallium selenide – a high efficiency semiconductor with a 10-23% conversion efficiency rate.
• Monocrystalline silicon shingles can reach 15-20% efficiency.

Both types of thin-film photovoltaic cells are durable and should last 20 or more years and come with lengthy warranties. The advantages of choosing solar shingles include:

• Maintaining the aesthetics of the roof. Whether choosing slate, ceramic tile, asphalt, or more modern oversized styles, solar shingles lay flat, as an integral part of the roof.
• It’s easier to work around roof fixtures like chimneys.
• Shingles require very little maintenance.
• The entire roof becomes a solar receptacle, rather than being limited to panel dimensions.
• You don’t need to make any structural changes that might be necessary with panels.

Shingles aren’t perfect. Most people won’t get the same efficiency rating as they would with panels; however, you are covering the entire roof instead of just a portion of it. The cost of a new roof, using solar shingles, will be significantly more than an asphalt shingle roof, even twice as much. Homeowners can plan on recouping much of the cost through tax credits and energy savings, so, if you need a new roof anyway, plan on staying in your location, and your roof is situated so that it could harvest a fair amount of sun, you might want to consider solar shingles. Shingles are a way to circumvent HOA restrictions on panels. While adding solar to your home increases its value, shingles aren’t something you can pack up and take with you when you move.

Solar Shingle Sources: Freesuns, SunStyle, GAF Energy Timberline Solar Roofing System, Tesla Solar Roof

Solar Windows

Solar shingles and panels both assume you have access to a roof. What happens if you live or work in a high-rise building? There are still ways to harvest other sources of solar energy. Solar windows could take advantage of the 5-7 billion meters of window glass in the US alone. This solar technology is still in its infancy, but products have been tested and are, or will soon become, available in Europe and the US.

Solar windows work a bit differently than panels because they can harvest ultraviolet and infrared light waves to create electrical current. The windows allow photons to pass through the glass so they look just like other windows. Currently, there are three materials that have been investigated for use in windows: quantum dots of semiconducting materials, luminescent solar concentrator materials like the luminescent particles found in food, and perovskite crystalline minerals compounds. The quantum dots and luminescent solar concentrator materials can act in consort to absorb different wavelengths of light. Tiny wires lead from the window to connect to the building’s wiring.

Perovskite crystalline mineral compounds are being investigated for use in both windows and solar paints. It can be produced inexpensively and is as efficient as silicon cells. Its downside is that it currently requires very small amounts of lead, and it has shorter longevity than silicon cells. (Perovskite is discussed further in the section on solar paint.)

Solar windows need to be manufactured with the technology incorporated, then installed. Eventually, it will be useful to create a coating that could be placed on existing windows transforming them into solar generators. This would reduce installation time and costs and negate the need to replace existing windows.

Michigan State University, with Ubiquitous Energy (UE), a leader in solar windows, has created a pilot program at 12 locations using 14” x 20” windows. UE is planning to build a production facility to manufacture floor-to-ceiling windows for commercial buildings and are partnering with Andersen Windows to produce windows for residential use. They anticipate that solar windows will cost 30-40% more than traditional passive glass, but this cost could be offset by tax credits, energy savings, and even selling energy back to utilities. Other US universities and groups, such as the Massachusetts Institute of Technology, are also exploring solar windows.

In Europe, the solar window leader is Netherlands-based Physee. Their first windows were installed at Dutch Bank in 2017 using food waste to absorb UV light and perovskite solar cells. They’ve been installing 15,000 Smart Windows in office buildings across Europe that are used to generate solar cells and sensor technology to help manage the building’s energy usage and comfort. They have succeeded in cutting energy costs by up to 30%.

With solar glass, skyscrapers have the potential to become vertical solar farms. Because they are vertical, they can capture some angles of the sun that panels alone wouldn’t capture. They would also absorb UV and infrared light that is bounced off other surfaces. By capturing both UV and infrared light, windows exponentially increase the amount of sunlight that can be transformed into energy. Eventually, solar windowed buildings could provide around 40% of the energy demand in the US, and if combined with rooftop solar units, almost 100% of the demand could be met. The greater surface space compensates for the lower efficiency rating of 10% that windows currently achieve.

Research is ongoing into creating solar window options. The University of Michigan is experimenting with plastic, semi-transparent light absorbers sandwiched between two planes of glass to capture the sun’s rays. An electrical port on the window frame would allow users to charge phones, laptops, or other devices using this captured energy.

While solar windows would be 30-40% more expensive than standard windows, their expected usable life is 50 years, and tax credits and energy savings can offset the cost. UE is expected to have windows for sale in 2025 or 2026. These windows wouldn’t be wired into the main electrical box, but could potentially be wired into battery back-up systems that would reduce reliance on the grid.

The same technology, which uses earth friendly, inexpensive, and abundant materials, that captures the infrared and UV light while allowing photons to pass through can be adapted for other purposes. For instance, cellphones or headphones could become self-powered, and a coating on car windows would help power the car. This coating technology is also the basis for developing solar paint.

Window Sources: Ubiquitous Energy, Physee, Andersen Windows, Solar Window

Solar Paint

Solar, or photovoltaic, paint is not yet commercially available, but it has huge potential. It takes any existing structure and without adding or changing anything to it makes it solar capable. It’s easy to apply and can be used on wood, brick, plastic, or any other material. PV paint includes billions of light-sensitive materials suspended in the medium to transform typical paint into a super-charged, energy capturing coating. Except for having a licensed electrician to wire everything into your system, this could be a DIY project. The technology exists, it just isn’t efficient enough at 3-8% efficiency to make it viable. Researchers are still trying to reach or surpass a 10% efficiency threshold before making it available. There are 3 technologies being explored.

Colloidal Quantum Dots: These are the same semiconductor nanocrystals that are used in solar panels, LEDs, and computers. For paint, they are luminescent molecules that are suspended within a flexible and sprayable liquid that will absorb light and moisture and convert it into electricity. They would capture a broader spectrum of light than traditional solar panels to harness the energy of infrared rays, making it more efficient. Potentially, it could be sprayed onto existing solar panels to increase their capabilities. To date, the US Department of Energy’s National Renewable Energy Laboratory’s (NREL) record for photovoltaic paint using quantum dot solar cells is 13.4% under testing conditions. When you change the size of the quantum dots, you change the light absorption spectrum. Optimally, quantum dots could be more efficient than traditional solar panels.

Perovskite: As mentioned above, perovskite is a crystalline mineral, derived from calcium titanium oxide compounds that can harvest light. While first discovered in 1839, it’s only been in the last 10 years that researchers in Japan debuted the first application for use in solar cells. In a near-transparent film, it can be used to tint windows, as a coating for roofs, or the sides of buildings. It could also be a replacement compound for silicon solar cells. This type of solar paint, in a transparent coating, could easily be integrated into paints, window glass, vehicles, and other types of building surfaces. This technology, used in conjunction with solar paint, would have ten times the conductivity of paint alone.

Hydrogen Producing Solar Paint: Hydrogen is a clean fuel source and globally plentiful. When the oxygen and hydrogen in water are separated it creates electricity, similar to how conventional photovoltaic cells work. The Royal Melbourne Institute of Technology has used synthetic molybdenum-sulfide in paint to absorb moisture from the air. Paint that includes titanium oxide, the “perfect white,” helps with the breakdown of the absorbed moisture. One of the advantages of hydrogen-producing solar paint, is that is can be used in any climate, whether sunny or not, as long as there is water vapor in the air to act as fuel. The disadvantage of this technology is that hydrogen needs to be compressed and stored properly, and needs to be kept separate from oxygen to make sure that an explosion doesn’t occur.

Although solar paint is not yet commercially available, its potential as an easy-to-use and produce product is enormous. It’s less energy-intensive to produce, uses fewer materials, and has lower emissions in production than traditional solar cells. It can be easily applied with a spray gun to surfaces of any size, shape, or material including plastics and fabrics. It can be used for fencing, sheds, mailboxes, and building materials such as wood siding, brick, or concrete. It can even be used to paint the sides of ships, taking advantage of light reflected off the water. Painting the roofs of buildings white would not only generate electricity, but would deflect the sunlight from the roof better than other types of materials. However, titanium dioxide sources are decreasing, so a substitute for it may need to be found.

There are still some other issues to be worked out with solar paint. It hasn’t reached an efficiency rate to make it financially or practically feasible. The current maximum of 7% isn’t sufficient to power an entire building, but solar paint could become one tool in an overall plan to be energy independent. Other issues to be resolved are its instability, requirement that it be stored in the dark, and short shelf life. For now, the University of Buffalo and the University of Toronto are both working on a spray substance that can be used on windows and solar panels to enhance their solar capabilities.

Solar Options that Work Independent of the Building

So far, the options we’ve talked about – panels, roofs, windows, and paint – have all been attached or an integrated part of the building. If none of these are feasible, for instance, if you are renting, there are still some options that are less permanent. You can take them with you when you leave and you won’t leave marks or alter on the structure. Many of the options only require an electrician for the wiring.

Free-standing sculptural Flowers/Trees: The most independent choices are free-standing, often nature-inspired solar sculptures. These aren’t intended to power an entire household, but can serve as a battery backup, provide some solar energy, or even be used to charge your electric vehicle. Depending on which version you purchase, Smartflower can fulfill each of these functions. All that is needed is 16 feet of clear space. This thoughtful design automatically closes in strong winds and has a smart cleaning function that brushes itself before it folds up. It tracks available sunlight so it can collect up to 40% more energy than traditional, stationary solar panels. It’s not light at 1,690 pounds, but it can travel with you to your next home. Sites like EnergySage.com or Solar.com calculate that the energy produced per watt costs more than the average roof system, but it’s a viable alternative to not being able to generate any solar power.

While solar trees can generate a fair amount of energy from their photovoltaic panels, they are sometimes installed more as functional art installations that supplements or acts as an energy offset, for commercial buildings, as street lamp power sources, or electrical vehicle charging stations. They aren’t as practical for home use because they currently cost about 4 or more times more than traditional roof panels.

Many manufacturers incorporate the panels as a shade feature for benches underneath. They can be seen at parks, zoos, and other public function locations.

Sources: Smartflower, Spotlight Solar, Solvis, Imagine Power Tree, Beam

Ground Mounted/Vertical Panels: Less sculptural, but more pragmatic, are ground mounted or vertically oriented panels. Because these photovoltaic panels aren’t attached to the roof, they can be either pole- or frame-mounted to sun-tracking technology that rotate to maximize sun exposure, like the Smartflower above. If one-sided panels are used, orienting them southward is optimal. If two-sided and stationary, they can be positioned to take advantage of the east/west axis and moved throughout the year to capture sunlight as it changes with the seasons.

Some of the advantages of moving panels from roof-mounts to an independent frame are:

• There may not be HOA restrictions if the panels can’t be viewed from the street.
• Vertical panels can operate at a lower temperature than traditional horizontal panels, increasing efficiency and potentially extending their lifespan. Vertical surfaces are better at dispersing heat. Efficiency increases of 2.5% are common.
• Vertical panels are better in limited space areas. They can even be mounted on the walls of a house or integrated into the building’s design.
• They may be better at capturing sunlight in off-seasons like winter.
• By placing panels vertically on a flat roof, you need fewer anchors and rails to create the necessary angle, and it’s easier to create a continuous row of panels.
• Because the panels are vertical, snow won’t stick as easily so they are more efficient in snowy regions.
• They are easier to clean and maintain.

Wherever space if very limited, vertical panels are a good choice, whether this is crowded urban areas or agricultural regions. They are also more practical than panels on uniquely shaped or narrow structures, or in equatorial regions where the sun remains high in the sky throughout the year. Vertical panels can double as noise barriers along highways, be part of fences, walls, or sunshades.

Mitrex is a company that has taken vertical panels to an advanced level. They create siding, building facades, solar railings, glass panels, noise barriers, or integrate their technology into parking garages. Many of their products are completely indistinguishable from common building materials. Some countries have begun experimenting with integrating solar systems with some of their infrastructure projects such as retaining walls and noise barriers. The Swiss canton of Appenzell Ausserhoden installed panels on a 75-degree retaining wall to help meet their 2035 goal of using renewables to meet their energy needs. The project didn’t require the use of land, snow doesn’t build-up on the mostly vertical panels, and it currently generates enough electricity to power over 50 households.

In Germany, apartment buildings have added panels to balconies. This project doesn’t require professional installation, residents just have to mount the 50-pound unit on the railing and plug it in. It isn’t as efficient as rooftop panels, but it doesn’t require additional space and you can take the unit with you when you move. The units are also available in Austria, France, Italy, and Poland. It can be plugged into the grid, or used as stored energy for personal use.

Sources: Next2Sun (bifacial modules), Mitrex, K2 Systems, Solarmotion, Balkon Solaranglage, Ertex Solar

Final Thoughts…

Using solar energy to help power your home isn’t limited to PV roof panels anymore. Research has created lighter, flexible, and more efficient ways to generate electricity from the sun, with new technologies and greater efficiencies emerging every day. Items like solar windows, integrated façade panels, or shingles are great options if you own, or are building, your home.

For renters and those with very restrictive HOAs, free-standing vertical panels, balcony units, or solar paint can be viable options. We are no longer restricted to unwieldy solar roof panels to help us power our lives.

If you are interested in adding a solar project, there are a number of solar calculators available to check whether it’s economically feasible. (See EnergySage.com or Solar.com)