SolaRoof | Phyto Tech

This section of the Wiki I will dedicate to Reinder van Tijen of Demo Tech, who works to benefit the poorest among us and so enriches all:

Reinder, I am very interested in your algae culture idea and it is a good example of the concept of using roofs more effectively. You are correct that I have thought about growing algae by using the roof area of a building - including homes and other structures. However the Sola Roof concept for Mass Algae Culture is not based on a roof pond idea. This is because the pond is too heavy and results in a more expensive structure to support the dead weight. Also, it is difficult to access the pond and to harvest the algae. And since a roof pond would not be in contact with the ground and is directly exposed to the thermal radiation of the sun (which is absorbed by water of more that a few cm. depth, then there is a serious tendency for the pond to overheat.

The Sola Roof Mass Algae Culture system:

The Sola Roof method is to provide a reservoir at ground level (a tank or below ground cistern) of an appropriate volume in relation to the roof area and we circulate the liquid (water with nutrients and algae) to the Sola Roof, where it flows over the surface area of the roof as a thin film. This thin film will not absorb so much of the solar thermal energy because it flows over a thin, flexible and transparent roof membrane, but the flowing liquid can carry the algae to the roof (the algae are free floating in the liquid) where the algae are well exposed to sunlight for a few seconds and absorb the PAR radiation. Algae that are in ponds are not exposed to the PAR, except when natural motion brings them within a few cm of the surface of the pond. This is a slow process and accounts for the lack of productivity of the natural pond. The Sola Roof design overcomes this problem by using a low energy circulation system that conducts the algae to the Sola Roof, which is designed to give a maximum but brief exposure of all the algae to the PAR (Photosynthesis Active Radiation) and the algae have a cellular mechanism to absorb sufficient radiant energy to use for several generations of cellular division (multiplication) which is the special Phytomechanism (growth mechanism) of algae. Therefore I call this Mass Algae Culture system "Phyto Technology?" or Phyto Tech at the Wiki.

The algae that have been exposed to the sun while flowing over the roof will drain with the liquid (by gravity) back to the reservoir where the multiplication will continue even though the algae are not in the sun - this is called the "bloom". Thus the biomass bloom forms in the tank, which can be of sufficient volume, but is supported on the ground or in the ground, so that the weight of the tank is not a problem. The tank construction is easy to integrate with the space available in the residential building because it is fundamentally different than a "pond" concept. I have used a tower tank that takes a small floor area but the tank has a height that reaches up to the roof level. Therefore there is almost no "lift" pressure for the circulation pump. This is a very good application of PV electric energy to grow the biomass and the load is perfectly balanced with no electrical battery storage requirement. To control the overheating tendency of the circulating liquid it is possible to pipe the liquid through some in-ground loops of flexible pipe for thermal exchange as the liquid is conducted to the roof. Other liquid to liquid thermal exchange is also easy to achieve and is very effective. The liquid flow path can be controlled and switched to obtain the proper control of the liquid temperature. It is important to note that a cool liquid results in maximum growth because the warm liquid will not absorb CO 2 and will therefore limit the growth and bloom of the algae. The circulation pump is a centrifugal type that can also harvest the algae from the flow - before it is sent to the Sola Roof. The pump skims off the algae in a process similar to the separation of cream from milk. The algae contain about 50% veggie fat (lipid)and so are lighter, as and therefore like cream they can be separated from the nutrient solution in which they bloom. The lipids are separated and can be converted to a Bio Fuel. Enough algae remain in the flow to be the "seed" generation and continue on to the Sola Roof to gain exposure to the sun while flowing over the transparent roof cover.

In this system the biomass density is much higher than any pond system and the rate of biomass multiplication can be 10 to100 times more rapid. Therefore the production of biomass can reach the theoretical limit of conversion of PAR, which is about 30% giving an overall efficiency of about 15% of total radiant energy being converted to biomass. This is higher than the best available PV technology. And it is much higher than other Biomass Crops can produce. Additionally, the PAR that is not utilized transmits through the transparent Sola Roof and can be used to grow other plants located beneath the Sola Roof – plants which have leaves. This is the recommended practice: - that beneath the Sola Roof there is a "net system" which supports an extensive leaf canopy that is the secondary absorption surface area for the PAR and for the total solar spectrum. This is due to the special capacity phytomechanism of the "higher plants" of transpiration, which is a natural cooling process. The leaf canopy will not overheat and remains cool. The Sola Roof will not overheat and remains cool due to the liquid circulation. This is a great benefit for the tropical regions.

In the tropical regions we can use single skin Sola Roof construction. A Poly Fabric? skin costs about 0.20 € and the structure framing is based on high efficiency geodesic dome design, space frames or almost flat, extensive roof areas built with light, Wide Span, open web joists. These efficient structure concepts can be built with many types of materials. We can build "tree-free" from recycled metal framing or use bamboo or modern high tech composite fiber materials. Therefore I would encourage you to consider a Sola Roof project in the slum community because it will be the lowest cost and highest value and can show a new pattern of Open Eco Design that is the foundation for a realistic opportunity to raise up communities out of their poverty. I only find it shameful that we in the wealthy communities are not motivated to build the Sola Roof pioneering projects that would become patterns that would save them from their planet destroying lifestyles and also provide a pattern for sustainable living that will be accessible to our brothers and sisters who live in poverty. I appeal to all those individuals with the resources to move ahead on personal Sola Roof projects for your own benefit (we are all lacking in our practice of sustainable living) or to fund Grass Roots Projects in poor communities.

As for the solar powered pumping - especial where we can avoid the need for "grid power" - that is very important. It is also very important for the Bubble Tech process (which requires a double layer Sola Roof envelope) and it would be fine to be able to blow the bubbles without any electrical energy being needed - that is, by using an air system. If you can also pump water with air pressure, so that no electrical motors or energy is required, that also is very interesting.

Reinder, I have just had a look at your wonderful Wiki and congratulate you on a great implementation of Pm Wiki, which makes it so easy for our communities to collaborate. I will add your Wiki homepage link to our navigation links - there is a growing community of communities that all Wiki together and speak the same Pm Wiki language. This is a great assistance to our global unity in action and supports our Open Source accessibility.

I look forward to our ongoing collaboration and I will place this information on the Sola Roof Wiki and add more pages in the near term

Demo Tech wrote:

Rick, hi!

… it is good to contact you, as I suddenly find myself involved in two concepts related to solar-roofs. Different from-, yet similar to your concepts. And I hope you will give me some feed back on it.

The dream

Everybody will agree that the most beautiful solution for the degrading lack of sanitation in the endless square miles of shanty towns around the globe, would be a system where human excreta is instantly recycled again into food. And this in a safe and clean way. To this end Demotech's approach started with the design of a private toilet-unit: the 'Bathroom Box?'. Then we envisioned a new (yet old) profession of excreta collecting and recycling. We used a mockup to find out how a collector cart could be hauled through a very densely populated slum and how a No-Touch filling system would work. Our feel was that the dangerous feces should be burned to ashes and that the rather safe urine should be 'fed' to algae in shallow ponds. As there would be no free space in such slums for the surface needed for these ponds, the obvious idea is to integrate the roofs people live under with the shallow ponds that best would be positioned higher up, to be safe from chickens, dogs, goats and playing kids. Harvested algae out of such modular roof-pond elements would be the high-end base for the localized production of carbon and proteins containing organic products.

Links to knowledge on algae

Well that is the dream! In your Solaroof-website algae ponds are mentioned, but no details given. In a mail of some month ago I asked you and some people that you had send some information to, if they had some idea about the use of Sola Roof structures for the breeding of algae, but I got no response. Since then the idea of Solar Sanitatition? fascinates me even more. I would much appreciate it if you can help me with the sources of info on algae that you know of. Or any comment on this idea that you could give. Of course Demotech already did some literature research. You can find our info at http://www.demotech.org/pmwiki/pmwiki.php/Design/D53 together with descriptions and some pictures of out experiments on follow-up pages.

Linking to your project out from an other design initiative: the 'Brick Stove?'

As it is cold around this time in the Netherlands, I am forced to think and work on stoves. Demotech develops the Brick Stove?, a challenge to combine a stove made out of stones and mud, that could becomes a high-end environmental performer when complemented by a high-tech add-on. Yesterday I described my ideas about this add-on at the following page of demotech's website: http://www.demotech.org/pmwiki/pmwiki.php/Design/D15UrgentQuestions

It is about an air pump, driven by a Sterling engine. This pump with drive is seen as a mass produced industrial product. It should create and control the flow of air though this Brick Stove?.

Today I realize that an almost similar air pump could be of value to the Solaroof concept. I wrote you before about some ideas how the idea 'Solaroof' could be realized at small scale for low income farming: a compact bubble generator unit of just sufficient power to insulate separate small shelters. This bubble generator should be light and handy enough to carry along form one shelter unit to the other.

I expect the Sterling driven air pump that I describe for the Brick Stove? could be modified into this light weight bubble generator. It then would need no electricity to run on, but energy from burning some rubbish could be used instead.

If you could endorse this idea, it can be expected that the double use of this Stirling air pump concept could boost its development.

I'll greatly appreciate to receive your comments. Kindly yours, Reinder