Solaculture: A novel biological approach for low cost energy?

[RCP]

This seems to be a very interesting low-tech system to harness solar energy. I would greatly appreciate any input, critical or supportive, from the many knowledgeable posters who frequent this forum. You can click on the link and watch a short video, or just read the description of how it works. For full comprehension I'd recommend both.

The inventor, John Popovich, has a long history in solar innovation. Back in 1975 he was developing unique solar collectors, and was the keynote speaker at an ERDA funded ISES conference in San Diego on testing solar collectors/systems. It was attended by then Governor Jerry Brown (start recursion loop) and then Mayor Pete Wilson, with a cast of experts in radiation physics and fluid thermodynamics. Many procedures in testing solar were altered as a result of his feedback at round table workshops. Now, after being diverted forming several companies and designing LED's, he returns to earlier ideas on passive solar systems. What problems do you see in implementing Soaculture, and are there any flaws in the concept itself? Looks good to me, but my knowledge of other alternatives along these lines is quite limited. Thanks.

Solaculture - A New Solar Economy

Solaculture uses “Fluidynamic Solar Concentrator “ (Patent Pending) technology to organize and control local thermal, aerologic, hydrologic, and biologic flows for the production of food, water, fuel, heat, and electricity. The technology provides a means to remove CO2 from the atmosphere for plant growth and for the sequestration of carbon as humus in the local Earth and a means to collect and store atmospheric water, evapotranspiration water, and precipitation water in the local Earth for plant growth and other uses. Biogas can be produced from methanogenesis within the Fluidynamic Solar Concentrator array via animals and/or via thermally accelerated decomposition of organic matter within the soil or from sources such as sewage, garbage, and agricultural waste and the biogas can be used to provide heat and electricity.

Solaculture arrays can provide very high solar concentration at low cost. They are composed of regions of land or water covered with porous canopies and a means to provide a slow downward airflow thru the porous canopies to reverse and control the typical buoyancy induced upward air flow resulting from solar heating and water evaporation. Plants in some instances can act as canopies and present the minimal cost Solaculture array. Solaculture can provide enhanced environments for people, plant and animal communities by varying the canopy and Earth properties, and the airflow rate and direction.

***[RCP]Below is the start of John's attempt to respond to each individual issue raised at Randi.net. I thought this first one might anticipate possible questions that might be raised here, and will introduce others if there is interest in this system.

I'll believe this one when I see it work.

I don't see how the solar heating induces a downward flow through the membrane, for starters. I would expect an upward movement, as the hot air rises. Certainly this is an arrangement similar to a solar chimney, and those capture the upward movement of air for energy.

Solar heating and evaporation do lead to upward airflow. It is possible to reverse the typical upward flow of air resulting from solar heating and evaporation by the use of an engine or a fan and/or via stack effect. Membrane may be a poor choice of words as it often refers to separation at the molecular level, not a subject of interest in this case.

If he's inducing an inward flow of air by means of a blower, the power has to come from somewhere. If it's coming from the turbine that moves the methane and air into the burner, then basically he'd be describing a jet engine, but the power neccesary to pull air through square miles of porous membrane would be immense and there goes your effeciency.

The force required to reverse the typical solar induced upward flow is very small and is determined by the planform area and the difference in density over the height of the column of air where the flow reversal is desired (deltaPA). The work required is equal to the force times the vertical distance traversed (FxD). The slightly subatmospheric pressure within the canopy causes air to flow thru the holes in the canopy in proportion to the number of holes and the inverse fourth power of their equivalent hydraulic radius (Darcy’s law for laminar flow). More holes mean lower resistance and more flow. The equivalent hydraulic radius of a hoop house or other manifolding means can be several thousand times the equivalent hydraulic radius of the holes in the canopy film and the overall hydraulic resistance is as a consequence almost wholly determined by the hole resistance with very little dependence on the distance between the hole and the fluid mover.

The fan power required in watts is equal to the pressure difference in Pascals times the flow rate in cubic meters per second. A temperature difference of 20 degrees C and a height of 1 meter imply a pressure difference of ~100 Pascals which would require a minimum of ~10kw fan power for the 100 m3/s flow rate proposed for the 100 hectare array outlined in the Solaculture website. Assuming other resistances and real world fan efficiencies, a 500% increase in fan power would result in a 50kw requirement, a small amount for a 100 hectare array with a 1000 Megawatt peak solar input (50watts fan power required per peak Megawatt solar input). A large portion of the populated latitudes receives 2000kwh/m2/yr and a peak solar input of ~1kw/m2. Averaging the solar input over the 8800 hours in a year yields ~225w/m2 or a 24hr annual average of 225Megawatts input for a 100hectare array.

He's talking about extracting methane from decompositon, and running the methane, plus the air that percolates through the membrane through a burner to power a turbine. Methane and air are flammable in mixtures from 5 to 17 percent at atmospheric pressure and reasonable temperatures, according to some brief googling. That's an awful lot of methane in a breathable atmosphere, and at the same time an awful lot of breathable atmosphere in a process that works best in anaerobic conditions. Trees may use carbon dioxide, but they also are aerobes and use oxygen. Keeping them in a condition where the leaves are in a mixture depleted in oxygen, and the roots are in a condition suitable for rot sounds rather implausible.

A large volume of gas in explosive concentration is certainly not proposed and control means to prevent such concentrations are important. One of the ways methane from landfills is utilized is called cofiring, where an engine driven generator is fueled by natural gas supplemented by methane. Methane produced from decomposition of organic constituents within a landfill may be able to provide a portion of the load but not required to provide stoichiometric proportion. It is also possible to provide a portion of the methane in the airstream and a portion of much higher concentration from a plumbing manifold within the local earth. Catalysts can be used to burn very lean methane/air mixtures and gas turbines (Brayton cycle) typically operate with 5X the air required for stoichiometric combustion, so there are several means to operate engines or furnaces without creating an atmosphere with explosive potential. Methane is produced by microbial processes in the Earth rather than by plants and some of it is transported thru the plants to the atmosphere but the bulk of the methane is transported thru the Earth to the atmosphere. Methane is not apt to react with plants as it is a very stable molecule (CH4), which accounts for its high Global Warming Potential (GWP). The atmosphere in the canopy may include increased CO2 from exhaust gas recirculation (EGR) to accelerate plant growth.

He talks about carbon sequestration, but this process is carbon neutral; he'd be using sunlight to make biomass, rotting the biomass to make methane and then burning the mixture and releasing it back into the atmosphere. he shows a condenser for the water, but water isn't the issue, or is a tangential issue. He's still releasing the carbon back into the atmosphere.

If the net plant matter is increased, the greenhouse gases CO2 and H2O are removed from the atmosphere, and if a particular Solaculture array that represents a net increase in plant matter is operated in a carbon neutral scheme, atmospheric CO2 and H2O are still lessened by the net increase in plant matter and the sequestration of water within the local earth. Additional CO2 can be converted to carbon and stored as humus, which also greatly increases the quality of the soil.

Water is a big issue for a number of reasons: it is an important greenhouse gas and groundwater is being rapidly depleted and introduced into the atmosphere, increasing the greenhouse effect. Groundwater stores are part of a hydrologic cycle with timescales of thousands of years and anthropogenic depletion of groundwater stores may have an importance similar to the depletion of hydrocarbon stores. The American breadbasket is rapidly depleting the Oglala Aquifer that supports it and the consequences may be troubling. Many regions cannot support agriculture due to lack of water so the ability to capture and recycle water is an important part of Solaculture technology. There is evidence that droughts have caused the demise of civilizations, including the Mayan civilization in the Americas, so a means to create drought tolerant agriculture would be attractive. It’s easy for us to forget that our own civilization is very dependent on agriculture since so few of us are required in that effort at present, but we may be cruelly reminded as others have been and all the computers and all the kings’ men may be for naught. The vast majority of solar radiation impinging on a Solaculture array serves to convert liquid water to gaseous water. Solaculture is primarily a mechanism for the organized evaporation, transpiration, transportation and condensation of water. Plants may absorb as much as 3/4 of the sunlight striking them but the vast majority of this energy is used to evaporate water. Plants used evaporation to pump liquid water and other constituents from the Earth and for cooling. The combined evaporation from the Earth and transpiration from plants is collectively called evotranspiration and it is the primary vehicle for energy transport in Solaculture.

This could plausibly be done (and is done) as separate cycles. It's an old hippie commune thing from the 'Other homes and garbage' days. Sun on grass or grain, plants in cows or chickens, critter waste in an anaerobic digestor, digestor gas to a turbojet. (more likely an old light plant engine, or even a lawnmower belted to a car alternator, but a turbojet would work. You can make a decent turbojet from a turbocharger.) The point is that all the steps in this process require their own individual conditions to work efficiently, or work at all. Putting all the bits in one container, and trying to find an optimum condition that'll let the whole thing work well is problematic. Finding a condition that'll let the whole thing work at ALL might be problematic.

Reductionism manifests itself in product design in the separation of function mantra, but clearly biota are examples of integration of function and this must be an indication of economy of means and worthy of our pursuit. Plants use their vasculature as structure and mechanism. It might be an interesting design exercise to try to design them with separation of function.

Consider a closely spaced hoop house array with perforated film enclosures and the interior volumes connected to the air intake of an engine driven generator. As the load on the generator increases, the flow of fuel is increased to maintain a constant generator rotation rate. If the air entering the engine contains some methane, it simply means that the control system will have to add less fuel to maintain a constant rotational rate. The conditions within the array may change with time and the amount of methane may increase in a mature Solaculture array or via the addition of organic media such as manure, sewage, or agriculture waste and less supplemental fuel may be required. It doesn’t seem like a wildly complicated scheme.

 

[Proton Soup]

i saw a guy writing on a dry-erase board. i don't see any working models.

 

[RCP]

Thought I'd give one last shot at getting some feedback on this idea. I admit it has been weakly presented, but on other sites Popovich was able to answer questions posed quite well. I'm still sort of on the fence, especially wrt how pragmatic the concept is. :(

 

[Proton Soup]

it looks like something that will consume more energy than it generates, that's what i think.

 

[LudusRex]

Certainly the process of growing plants, harvesting them and transporting them to an engine driven generator would be complex and costly in comparison. The array would be designed to provide an environment conducive to plant growth and the production of methane. The engine driven generator might be designed to provide an environment conducive to efficient combustion of methane and the production of electricity. The efficiency of the array and the engine driven generator might be optimized by the design engineer who might be able to maximize the energy output of the array and the engine driven generator, and the efficiency of the array and the engine driven generator might be optimized by the operator who might be able to adjust the conditions within the array and the engine driven generator. The operator might be able to adjust conditions within the array and the engine driven generator to optimize the production of methane and the production of electricity. The operator might be able to adjust conditions within the array and the engine driven generator to optimize the production of methane and the production of electricity and the production of plant matter. The operator might be able to adjust conditions within the array and the engine driven generator to optimize the production of methane and the production of electricity and the production of plant matter and the quality of the local Earth.

The quality of the local Earth might be improved by the addition of organic media such as manure, sewage, or agriculture waste to the array or the local Earth. The production of methane might be optimized by the addition of organic media such as manure, sewage, or agriculture waste to the array, or by the addition of organic media such as manure, sewage, or agriculture waste to the local Earth. The production of plant matter might be optimized by the addition of organic media such as manure, sewage, or agriculture waste to the array, or by the addition of organic media such as manure, sewage, or agriculture waste to the local Earth. The production of electricity might be optimized by the addition of organic media such as manure, sewage, or agriculture waste to the array, or by the addition of organic media such as manure, sewage, or agriculture waste to the local Earth.

The quality of the local Earth might be improved by the addition of organic media such as manure, sewage, or agriculture waste to the array or the local Earth. The production of methane might be optimized by the addition of organic media such as manure, sewage, or agriculture waste to the array, or by the addition of organic media such as manure, sewage, or agriculture waste to the local