When considering solar power, most people think about solar panels on a roof. While those work well in most circumstances, there are other options.  At the 2022 Washington Solar Summit, Solar Washington Board Member Chris Muench invited Ian Robinson (Northwest Electric and Solar), George Thomas (ClearVue) and Ian Lucas (A&R Solar) to discuss those options and ideas.

Maximizing Roof-Mounted Solar Power

Roof-mounted solar is a good way to harvest energy from the sun, said Ian Robinson of Northwest Electric and Solar, though its full potential is limited by factors such as the pitch and condition of the roof, shading and trying to keep panels clean.

The process to install solar panels, further outlined here, should start with understanding how much power is needed. To find out how big their system needs to be to reduce or eliminate their utility bill, consumers can use a year of utility bills to do a calculation. Solar companies can run a performance simulation, panelists said. Most people need 9-12 KwH to offset electricity usage, though larger homes or homes that use an EV are going to need more.

The next step is to research and seek quotes from several potential (and preferably local) companies before selecting the installer, and then working with the installer to design the system and identify all possible incentives.

The extension of the federal income tax credit for the next 10 years and the increase in the credit to 30 percent make solar more attractive. Homeowners also benefit from net metering, whereby the utility company gives credits for overproduction during the summer when homeowners “bank” kilowatt hours and applies those credits when the home is underproducing during the winter. Washington does one-to-one crediting, so homeowners get the full value of the credit rather than the 20 percent or 30 percent in some other states. Also, Washington State does not charge sales tax on any solar- or battery storage-related investments.  The designer should clearly show the estimated production levels and the benefits solar provides. 

While installers have “been rocked a bit” due to supply chain issues, lead times are getting shorter as manufacturers are better able to supply solar systems.

An advantage of roof-mounted solar is that it’s part of the building and the aesthetics can be better than other options. Panels fit the shape of the roof, and the thick underlayment helps with thermal insulation.

Ground Mounted Solar Array

If a landowner has enough space, said Ian Lucas, solar design consultant at A&R Solar, a ground mounted array could be ideal. It can be set to the exact orientation and tilt to optimize the panels. When panels are not on the roof, where it is 20-30 degrees hotter, the electronics will operate more efficiently.

The drawbacks for ground mounted arrays, he said, are that they are more expensive, need support for the panels and may require a trench for the wires. It is also important to check whether local guidelines and regulations allow ground mounted solar.

Homeowners will need permission from the local government for both rooftop and ground mount solar. Most jurisdictions are backlogged, so approval can take 3-4 weeks. Lead times for installations have also risen, from about 3-4 weeks for ground mount to two months and to 3-4 months for rooftop solar.

There will eventually be moveable ground mount solar and homeowners will get more energy yield because they follow the sun, panelists said, though more moving parts can mean that there are more potential points of failure.  While not yet commercially available here, a SmartFlower is a sculptural example of a moving ground-mounted system that rises in the morning and follows the sun during the day.

Financial incentives are the same for roof mount and ground mount solar.

Photovoltaics Windows

Another option is photovoltaics (PV) windows, which is glass that is part of the building rather than a solar panel . You can see through the glass, which generates energy, has triple glazing and uses a coating. These solar windows distribute infrared light to the perimeter of the glass and convert ultraviolet rays (UV) to infrared (IR). The glass reduces UV coming into the building, so it can reduce fading of furniture and increase solar heat gain.

While not yet available residentially, ClearVue’s system generates 3-4 watts per square foot and adding more solar cells with spandrel may increase electricity generation to about 12 watts per square foot. The maximum window size is currently 5 feet by 10 feet, which Thomas said is standard for a downtown office building.

Most solar estimate tools deal with rooftops, so calculating estimates for PV windows can be a challenge. ClearVue developed its own calculator using an API from PVWatts that uses factors such as carbon intensity, energy cost of the utility and the zip code. The firm can also calculate the kilograms of emissions per KwH and estimate the reduction in Scope 2 emissions. 

Tips and Trends

Solar panels produce direct current (DC) electricity and homes run on 240V alternating current (AC), panelists explained, so homeowners need an inverter that takes what the panels produce and converts it to utility grade power or pushes overproduction to the grid.

When one participant asked when they need backup batteries, panelists said the grid is like a hyper-efficient battery when there is net metering. The main reason for a battery is for resilience when there is a grid outage. They are also useful in states such as California, where electricity charges are based on the time of day and batteries can have a better return on investment. Consumers are able to run on a battery at night, which makes their home more green. If the grid goes out, a house without a battery will not have power because utilities do not want electricity production that can electrocute the lineman.

Key trends, panelists said, include adding a battery to the unit, or, as in the case of solar windows, using fans to move air in and out, and developing off-grid methods for use in remote locations.

And vehicle-to-grid and vehicle-to-home electricity could become available in the next three years. Vehicle to Grid (V2G) is a way of providing power stored in car batteries back to the grid in times the grid needs extra power. More interesting for homeowners is Vehicle to Home (V2H) when car batteries are used as the backup batteries of the home instead of using dedicated batteries like the Tesla PowerWall.

Still in the very early stages, smart panels will control how a home uses electricity, especially for homes with energy storage. The panels will optimize power usage for homeowners.

To hear the complete discussion, watch the recorded session here: