Cutting Costs With Solar Walls

By John Lorinc
Solar WallConserval Engineering A solar wall creates a cavity where sun-warmed air is collected, and then vented into the structure.

Amidst the general gloom in the renewable energy sector, one energy company based in Toronto is discovering a renewed appetite for a low-cost, low-tech solar air heating system based on one of the immutable laws of physics: hot air rises.

Conserval Engineering, which has offices in Buffalo and Paris, is responsible for SolarWall panels, made from corrugated and perforated galvanized steel. The cladding is affixed to south-facing walls of industrial and commercial buildings, creating a cavity in which sun-warmed air is vented up and into heating ducts.

Such systems reduce heating costs by cutting natural gas or electricity consumption – an important consideration for financially-strapped companies like the Ford Motor stamping plant near Buffalo, N.Y., that figures it’s saving $300,000 a year thanks to a 50,000 sq..-ft solarwall.

“We’re seeing a significant uptake in small to medium-sized projects,” said Duncan Coutts, Conserval’s vice president for international sales and market development.

And with companies looking at ways of reducing overhead costs to stay in business, Mr. Coutts said, “For us, the sun, the moon and the stars are coming into perfect alignment.”

Conserval officials claim the return-on-investment window for a typical installation is under three years. The capital outlay, they add, compares favorably with other solar technologies: a one-meter square panel yields about 600 watts of energy and costs about 80-90-cents installed. A similarly sized photovoltaic solar panel generates one sixth of the power, but costs ten times as much.

Quite apart from the cost benefits, such fixtures underscore the effectiveness of passive solar design, which is becoming an increasingly important tool in sustainable architecture as designers leverage features like building orientation, overhangs and wall-thickness to boost energy efficiency.

Mr. Coutts’ bullishness is rare in any sector these days, but Conserval is coming off a strong year, completing major projects in Canada and the United States, including one at Fort Drum, a United States army base in upstate New York. Last fall, Conserval completed the construction of 50 solarwall systems on 27 military buildings.

The company says the 110,000 square-foot installation will generate 4 megawatts of thermal energy and displace 2,000 tons of CO2 annually.

Other high-profile clients include the Beijing 2008 Olympics and the newly-opened John Molson School of Business in Montreal.

The company’s technology enjoys an endorsement from the Department of Energy in the United States, and its energy efficiency rating is verified using Retscreen, a third-party assessment protocol developed by the Canadian government.

If there’s a dark cloud to Conserval’s silver lining, however, it has to do with a proliferation of black market imitators. In January, the company settled a trademark violation lawsuit against another manufacturer, but its Web site still warns customers to watch for “knock-off versions.”

Comments are no longer being accepted.

Richard February 17, 2009 · 9:25 am

Editors and readers, please, please, learn the difference between power and energy, watts and watt-hours. And in this case, whether or not the numbers you cite make any sense.
Certainly, if I could buy PV panels at less than $10/sq meter, or even plain sheet steel for less than $1/sq meter, as the article says, I’d rush out and do it. Lots of it! Also, the technical reader may note that the claimed efficiency seems to be very close to 100%, which might almost make sense if one side of the wall wasn’t outdoors, and if your building happened to pivot to face the sun. There’s a little physics here.
Convective wall systems like this have been around for centuries, patented or not, but are seldom seen in
residential construction because of related issues with moisture, cleaning and maintenance, and the modest heat gain in winter relegating the use to preheating ventilation air, which generally is not deliberately supplied in a house. Best use would be on well-insulated, tight, large industrial buildings with careful siting and fairly complex hot air heating systems.

Michael February 17, 2009 · 11:02 am

Richard – have you looked at their website (www.solarwall.com)? You seem to be more then a little confused, the claimed efficiency of the SolarWall is up to 80% depending on location and southern wall exposure, which for solar thermal is realistic and verifiable (vs ~15% for PV…) Take a look at some of the projects on their site – WalMart, 3M, FedEx, Ford, GM, US and Canadian Military, NASA, the US EPA (Environmental Protection Agency), Boeing and on and on… No offense, but you do not know what you are talking about with moisture/cleaning/maintenance issues. This is simple, almost zero maintenance (view a Parks Canada Government video on the Solarwall //www.youtube.com/watch?v=KolGt8OW5xU) solar technology – I love hearing about successful green tech companies, and if we are to move away from fossil fuels and make substantive efforts to combat climate change we need more of this type of innovation! Great post, very informative!

Homemade Wind Generator February 17, 2009 · 11:54 am

It makes sense to get your numbers right, as Richard sites, this is the most easily misunderstood part of any renewable energy system, we see it all the time when people first build their own homemade wind generator.
Good article though.

CGC February 17, 2009 · 3:30 pm

Tapping Thermal Difference in the Design of Passive Solar Designs

It should be noted that the geographic location must be emphasized when considering the efficacy of technologies, such the solar wall proposed in this article, in the design of “Passive Solar Buildings”. It appears from the illustration provided that heat exchange occurs mainly between the wall interface of the inner and outer region of the building.

Will it be as efficient in “hot arid” regions, or “hot and humid” regions or during specific seasons of the year when the temperature outside is “quite hot”? What is he impact of microbial growth, e.g., molds and other fungi, inside and outside of the building under hot and humid environments?

An alternative approach, that is likely more costly, involves a “geothermal heat exchange” by tapping the significant difference in temperature (thermal gradient) of the earth and air atmosphere all year round — even in the hotter to colder regions. Moreover, the “earth and air” thermal gradient is more pronounced and greater than that present at lower and higher level of the air surrounding a building. As a result, the “geothermal” thermal gradient may be used more effectively to control both the degree of hotness or coldness of the inside air in the building through controlled exhange of heat betwen the incoming outside air passed through the underground pipes with the air inside.

In airtight buildings, using mechanical heat and cooling system, loss in heat (or cold) in the indoor air is minimized through minimal infusion of fresh air. The drawback of airtight buildings is the accumulation of indoor pollutants generated by the inhabitants, the buildings and appliances exhausts. These pollutants can trigger what is called “sick building syndrome” that can be debilitating and even trigger fatal illnesses. Airtight buildings may be susceptible also to termite infestation if moisture development occurs within wood structures.

In contrast, the “geothermal approach” to control indoor temperature year round allows sufficient fresh air coming in, as well as employ HEPA filters, to trap particulates and microorganisms. The “controlled fresh air refresh combined with HEPA filter” in the “geothermal approach” not only conserves energy but also minimize “sick building” syndrome.

The goal of passive houses designed in Germany, for example, attempted to achieve an inside atmosphere that would be comfortable all year round. [Visit //passivhaustagung.de/Passive_House_E/passivehouse.html This approach ensures that there will be a simpler and less heavy during heating and cooling system.

The alternative “geothermal approach” presented here must consider the geographic location. For example, it may not be suitable in areas where constant flooding occurs.

Uncle B March 20, 2009 · 1:02 pm

The end of the “cheap oil era” is bringing back many of the earlier ideas on passive solar heating. Does anyone remember heating pits full of cleaned rocks for evening heating? Can we send heat into the ground, then retrieve it at will? Any articles to recommend? Will my “Greater Depression” (GD) survival shanty complete with composting and humanured garden plot seem so out of place in a year or so? Remember those old storm windows you threw out? I use them for my greenhouse now, and the price was right -Free!