SLP Legacy Series: Modified Trombe Wall

Many visitors and employees alike have passed by the glazing on SLP’s Folger Avenue office and wondered: is it a solar panel? Is it a solarium? What is that magical thing? Well, it’s a Trombe Wall of course! A Trombe Wall uses passive solar principles to help heat our front office which reduces our heating bills and lowers our carbon footprint. The original wall was installed c.2005 and it was refurbished in 2019. Here’s a Trombe Wall tutorial for your reading pleasure.

The best, most cost effective implementation of solar energy is through a passive solar design, which is defined as the design/orientation of a structure to utilize the sun to heat or cool without mechanical equipment. Our ancestors understood this concept very well when they oriented their caves facing south. The low winter sun entered the dwelling and heated the space while the hot vertical rays of the summer sun were blocked, which kept the space cool. Fast forward to the 1960s and we encounter Frenchman Felix Trombe who was fascinated by how thermal energy could move via radiation, conduction and natural convection. His continuation of American Edward Morse’s earlier work in the 1880’s spawned the wall concept that now bears Trombe’s name.

Trombe walls come in variety of designs. Imagine sunlight coming through a south facing window and warming a concrete wall or other thermal mass during the day. At night, the wall releases its heat and warms the living space. Trombe walls can be truly passive with no mechanical equipment but in our application an air handler was installed to help accelerate the process by forcing air into the office through louvers located near employee’s desks. Utilizing the greenhouse effect, the clear Lexan panels on the front of the building allows visible light to pass through and strikes the dark front surface of the black metal corrugated panels. This radiation is absorbed and re-emitted as longer wavelength radiation which cannot escape through the Lexan glazing and heats the space. When a sensor registers that heat is available, the fan unit turns on and pulls air along the backside of the metal corrugation from two large intake holes located low on the wall across from our reception desk. This fan helps to speed up the natural convection loop and pulls cooler air up alongside the hot metal corrugation. The metal serves as a basic heat exchanger and warms the interior air as it passes by on its way back into the office. In the summer, the top flap of the Trombe Wall can be opened to let out excess heat.

The Trombe wall has served us well over the years, and has reduced greenhouse gas emissions while saving us money on heating costs. Due to the slow and steady nature of passive heat gain, Trombe walls work best for spaces that are inhabited between Noon and 10:00 pm such as a house as opposed to most businesses which open and close much earlier.

Sun Light & Power started out as a solar company designing and building solar hot water systems. That hot water was stored and used to heat space, spas, hot tubs, swimming pools, potable water, and in some cases process heat. In the early 2000s we added photovoltaic systems to our growing list of renewable energy offerings. Solar electric projects now constitute over 75% of our business. Today, August 6, we are celebrating our 44th anniversary. We are proud of the fact that Sun Light & Power is still providing innovative clean energy solutions for our customers and communities across California.

Jesse Quay is Senior Project Developer and a Vice President on Sun Light & Power's Board of Directors.

Next week Jesse will mark 17 years of dedicated service at Sun Light & Power!