Other Meteorological Reactor variants and typesSolar Updraft Tower Algae Biosphere by James A. Bowery (2006)
There is a great need to radically decrease the per person ecological foot-print of developed economies, world-wide -- a need to radically increase carrying capacity while reducing impact on high biodiversity ecosystems such as the Brazilian rainforests or continental shelf fisheries, and reduce concerns about global warming. There may be an economic option that uses sea water pumped to desert areas powered by the fact that ground level temperatures are much higher than temperatures at high altitudes. Indeed, it would dump greenhouse heat to space for its power while producing biodiesel, electricity, fish, fresh water, salt and real estate -- all in quantities demanded by developed-world populations -- without adding to, and possibly even sequestering, greenhouse gases.
Proposals for solar updraft towers have typically assumed that they would be single use structures: solar to electricity via heat differentials between high altitude air and ground level greenhouse-enclosed air. The resulting system has marginal economic value.
Something which would radically enhance the value of the solar updraft tower power structure is to use the greenhouse area for algae ponds to add biodiesel, water, fish and salt production to the production of electricity normally envisioned.
An objection to this combined use of the solar updraft tower is that the heat of vaporization lost during evaporation will translate into a lower temperature differential between ground and exhaust at the tower head. However, this ignores the recapture of that heat upon condensation -- a phenomenon that drives powerful natural phenomena such as thunderheads. The main problem, and it is a difficult engineering problem, is constructing an appropriate condenser at the top of the updraft tower. (One approach to the condenser problem may be to use Floating Solar Chimney technology as an alternative or in addition to the fixed tower).
Doing so brings the proposal from marginally viable to viable, with a net present value, primarily from live fish production, of $3.5 billion per system, thereby allowing for far higher capitalization and/or return on investment.
James Bowery idea of associated solar chimney with biodiesel algae culture
After calculation given in his webwite James Bowery
concludes that his project compares very favorably with the estimated construction cost of the reference tower of $500M to $700M, which, of course, will have to be increased to account for the addition of a condenser to the tower, pond construction, centrifugal algae harvesters, boidiesel equipment, aquaculture equipment and brine transport systems. Indeed, the construction estimate for the reference system can be quintupled and still be financially sound if the already moderate technical risks are reduced.
Thus we have a system that is potentially profitable in the early stages of deployment, and that provides self-sufficiency in terms of high quality protein and water, with industrialized-nation levels of energy in the form of electricity and biodiesel -- all in an ecological footprint of 1/100 gha percapita. The primary remaining barriers to providing a standard of living comparable to the current US level are in secondary nutrition sources such as produce (fruits, vegetables, etc.). As it turns out, the waste product from fish processing is a high grade fish emulsion fertilizer for such produce, and can support high density hydroponic gardens grown in the aquatic recreation areas and even residential areas at the outer rim. If this proves insufficient, the expanded ecological footprint to support a wider variety of produce is unlikely to more than double the total footprint, and we are still looking at a 1/50 gha percapita -- resulting in the entire ecological footprint of the US population being something like the size of Florida (rather than half its size as is South Carolina). Of course, this ignores the potential to let people harvest naturally occurring produce from the greatly expanded wilderness areas resulting from the contracting ecological footprint. From a tourism and recreation standpoint it is precisely such wilderness areas that provide expanded opportunities for people to live-out hunter-gatherer behaviors that seems to drive so much of the tourism and recreation industry.
Tom Bosschaert (from Except in Netherlands)
Possibility of solar chimneys expansion of potential: for Co-generation Use
Other solar technologies, such as collectors that use solar radiation to convert water to steam or photovoltaic (PV) arrays, generate substantial excess heat. In the case of PV, high temperatures diminish their power generation capacity. Using the solar updraft tower in combination with solar collectors or PV arrays can improve the efficiency of both systems. The constant wind flow can air-cool the collectors while increase the energetic output per area of land used, making the solar updraft tower a more efficient proposition. Things to consider in terms of the efficiency of combining these systems include the loss of some direct solar radiation as a result of its deflection by the membrane, and the amount of cooling that can ideally be achieved.
This strategy can also be combined with agricultural uses, where solar collectors or PV arrays would be placed at the center of the collector, where the winds are too strong for plant growth.
Illustration of Co-generation Solar Updraft Tower
Possibility of solar chimneys expansion of potential: for Urban Use
A completely different alternative use is the urban application of solar updraft towers, which is not necessarily conceived of primarily for its energy generating capacity. A tower in a city could hardly be the size of one in a field, so its generative power would be diminished. However, it could provide three distinct advantages alongside electricity generation.
First, the tower could be fitted with particulate, carbon and other air filters. The air rushing through the chimney would thus be cleaned resulting in urban air quality improvement, while at the same time generating some electricity. Systems like these would be very suitable for highly polluted cities.
Second, in cold climates, the heat dissipation of the urban environment can be buffered. The trapped heat will aid the power generation, but will also reduce the temperature gradient between interiors and exteriors, resulting in energy savings for building heating and higher insulation efficiencies.
Third, in hot climates, a second layer with a semi-transparent PV membrane could be installed. This would partially block out the sun, causing the temperature gradient to drop. There will then be two layers generating convection, possibly increasing the efficiency of the tower. The top layer would ensure the heat is not trapped in the bottom layer, thus preventing the heating up of the city. The constant air pull of the solar updraft tower will partially combat the heat island effect.
Illustration of Solar Updraft Tower urban use to clean te air
Possibility of solar chimneys expansion of potential: for Agricultural Use
An important side effect of placing a large transparent membrane over an area of land is the capture of evaporated ground water and its return back to the topsoil. This localized increase in land moisture can make the soil underneath the collector suitable for agricultural uses, through the effective creation of a partial greenhouse. In some cases, the land under the collector would not have been agriculturally viable without the presence of membrane. This means that certain barren lands could be reclaimed for productive use, making this energy generation strategy more economically favorable while also building agricultural capital.
The clearance height underneath the collector can easily accommodate farm equipment, and the supports for the collector can be far enough apart to allow the working of the land. Different kinds of crops can be planted depending on the local soil and moisture conditions, bearing in mind that the area near the center will have airflow too strong to allow plant growth. If the vegetation is very substantial, it may impact the output of the tower due to wind drag. However, increasing the distance of the membrane from the ground can mitigate this.
Another potential agricultural use is the application of algae growth tanks underneath the membrane of the tower. Closed culture tanks for biofuelproduction using for instance Botryococcus algae or open culture tanks with Spirulina as a nutritional source could expand the potential of the land to a large degree. Tanks underneath the membrane can then function as thermal storage to reduce the effect of diurnal swing as well. The water for the tanks can use rain water collection performed by the membrane, as well as ground water. In desert situations salty groundwater can be desalinated using solar desalinators also underneath the membrane, depending on the water conditions and the type of algae grown.
Using agriculture in combination with the updraft tower this system can be applied as both a sustainable economic strategy or for community restoration in developing nations.
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