I was talking with RE Hogan at Greenfire Farm this morning (before the team was continuing the work today on the POD footings) and RE was saying how some half of the USA is now reaching a stage of emergency drought conditions and the summer heat wave is continuing. Therefore, one of the powerful capacities that will be observed as the POD becomes operational is the cooling power of the Sola Roof technology.
There has also been a discussion of the thermodynamics of Sola Roof for solar heating and for "natural" cooling (which is low-energy) at the Yahoo Forum, with one of our members, Nick Pine. I have just wrote an answer to one thread of discussion about our POD project in Athens, Ohio (at Greenfire Farm) and I thought I would post it here as well:
Re: Athens December solar energy budget Thread with Nick Pine [subject is morphing into a hot weather/cooling topic]
Nick, is it possible for you to join us at Greenfire Farm this summer? If you could see the actual Sola Roof operational results you would be able to visualize the process and help us to correctly understand what is going on. Within the POD Prototype we have the empirical results that you can evaluate by going back to basics. For example, we accomplish everything required for cooling during the day, with no ventilation and no fans or circulation and no other components added - we simply have the plant canopy to intercept the sun-light (there is always a mature crop from which we are harvesting with junior plants growing, in the shade, to replace them) and convert the solar radiation with the two phytomechanisms, photosynthesis and transpiration.
These processes with billions of years of intelligence are so efficient that the leaf will remain cool while processing sunlight to carbohydrate and while emitting from 1 to 2 lbs of water vapour (per FT 2? of leaf area in sun) that is 100% effective for "waste heat" rejection in the form of latent heat of vapour to the closed atmosphere of the POD. Then, with no circulation fans or any other device this partial pressure of vapour in the POD "sees" the inner glazing as a vacuum and moves to this surface to condense there and release the latent energy to the cooling liquid flowing on the opposite side. Our only requirement is to maintain this surface at the desired Dew Point temperature, which is in a range from about 65F to 75F for tomato plants, and cooler for most leafy plants. This is easy to do. With the POD having within its construction a Liquid Thermal Mass (LTM) system that is about 1200 CU FT we have a relatively small temperature change per day. In the winter we can intentionally accumulate the sunny day gains and in the summer we cool down over night. This diurnal cycle is simple, cheap, low-energy and it is enabled by the efficiency of the Liquid Bubble Insulation and Shading which is well integrated with the Liquid Solar processes of daytime cooling (controlling both temperature and humidity) and heat capture and the night time chilling.
We see all of these processes working and producing the anticipated result in the Sola Roof projects that are built according to these simple specifications. Why imagine anything more complicated when simple gets the job done? Why look for a 40F (cold) for cooling or for very hot temperature for heating, when a "cool" and rather steady LTM will get the job done without any fans or tubes in soil or whatever? Just build the Sola Roof cavity space glazing and incorporate a large LTM (easy and cheap) and you have the solution you are looking for - which is great year around, low-energy, fresh and organic food. - Sola Roof Guy