When it comes to building energy efficiency, the roof plays a crucial role. A popular strategy to enhance this efficiency is the use of cool roofs—roofs designed to reflect more sunlight and absorb less heat than standard roofs. But what happens when you add solar panels to the mix? And how can vertical solar panels optimize your building's energy performance? Let’s dive into these questions.
What are cool roofs and why are they important?
Cool roofs reduce the need for building cooling and reduce the urban heat island effect. They are designed with materials that reflect more of the sun's rays and release the absorbed heat more quickly, keeping buildings cooler and reducing the need for air conditioning. Cool roofs are especially important for buildings with a high cooling need, like data centers and cold storage warehouses.
A cool roof can be made of highly reflective or white roofing membranes, different types of paint, a sheet covering, or highly reflective tiles or shingles. These materials work by increasing the roof's albedo—a measure of how much of the light that hits a surface is reflected without being absorbed. The higher the albedo, the cooler the roof remains, which translates to lower cooling costs and a reduced environmental footprint. With the different options available, a building renovation project can easily include a cool roof retrofit.
The impact of traditional solar panels on cool roofs
While cool roofs are excellent for reducing heat absorption, their benefits can be compromised when traditional solar panels are installed on top. Conventional solar panels are typically mounted at a nearly horizontal angle and cover large portions of the roof. This can turn your reflective cool roof into a black, heat-absorbing surface, essentially nullifying the cooling effect. Solar panel temperatures can easily reach up to 70 degrees C during hot summer days!
When a cool roof is covered with traditional solar panels, the roof loses its reflective properties, as the dark-colored panels absorb sunlight and increase the surface temperature. This not only undermines the purpose of having a cool roof but also potentially increases the heat load on your building, negating some of the energy savings provided by the solar panels.
Vertical solar panels are better for cool roofs
This is where vertical solar panels come into play. Unlike traditional horizontal panels, vertical panels don’t cover the roof, so the roof itself is not heated in the same way as with conventional solar panels. The high albedo of the cool roof is also a huge advantage for the energy production of the vertical solar! Let’s explain these benefits more in depth:
1. Maintain the cool roof function with vertical solar panels: By keeping the main surface of the roof uncovered, vertical panels allow the cool roof to maintain its reflective properties, ensuring that the roof continues to reduce heat absorption and keeps the building cooler.
2. Lower solar panel temperature: Vertical solar panels have a more efficient heat exchange with the air since they radiate heat from both sides, which contributes to a lower solar panel temperature. This has been confirmed by researchers from TNO in The Netherlands, and Over Easy Solar’s own measurements shows that temperature of vertical solar panels normally stay at only 10-15 degrees C higher than ambient temperatures during sunny summer days, about 10 degrees lower than for conventional solar mounting. This maintains the cooling effect of the roof and keeps the efficiency of the solar panels high.
3. Higher energy output: Vertical panels capture reflected light from the roof. This is why the increased reflection from the cool roof can significantly boost the energy output of the panels. In fact, simulations and measurements conducted by Over Easy Solar suggest that a high-albedo white roof can enhance the energy yield of vertical solar panels by up to 40% compared to a black bitumen roof!
Maximizing energy efficiency of buildings with cool roofs and vertical solar panels
By combining cool roofs with vertical solar panels, building owners can maximize their energy efficiency, maintain lower building temperatures, and even boost the performance of their solar installations. This innovative approach not only helps in reducing energy costs but also contributes to a more sustainable and environmentally friendly building design. If you're considering solar panels for your building, vertical installations on cool roofs could be the perfect solution to optimize both your energy production and your building's thermal performance.
