AuthorTopic: Synergestic Solar System  (Read 883 times)

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Synergestic Solar System
« on: November 18, 2012, 08:27:15 AM »
My apologies for my total half assedness on this, but hopefully if someone is actually interested in what I am proposing I can explain and back up with calculations and proper explanation.....

11-12-2012 1-48-39 PM
Solar Thermal Plant

The conceptual plant above consists of two closed loop systems that are integrated to promote symbiosis.  These two main systems are the steam cycle and the water cycle.

Steam Cycle:
The steam cycle has two primary functions, to produce electricity and heat.  This particular cycle is designed to operate as a baseload micro plant.  Its hybrid fuel source accommodates variations in seasonal solar inputs through the ability to efficiently generate from biomass or fossil fuel sources.

Caveat: As illustrated above this design operates around low temperature solar energy.  The premise and for this is at this point theoretical, though there exists promising historical data points to suggest it to be a very worthwhile approach to investigate (see Shumar vacuum solar engine).  Should this concept however not prove effective, the integrated plant concept could still be realized economically through either integration around an organic rankine cycle or a conventional concentrated solar power steam cycle.  I have choosen though to illustrate the integration concept around the novel low pressure steam cycle because I believe it could lead to the most dramatic cost breakthroughs as well as the widest area of impact.

   Condenser: The condenser is an industry standard heat exchanger designed to operate at 1.5psia of pressure.  Cooling water is provided from the aquaculture pond, temperatures from this pond will be moderated to an average 75 deg in most climates.  After initial evacuation of noncondensibles nearly all vacuum is provided by the condensing of steam into water in this closed heat exchanger.  From here the condensate is pumped to the low pressure solar boiler.

   Condensate Pump:
The condensate pump will sit in a deep well to provide needed net positive suction heads, its discharge pressure will be marginally above the cycles maximum pressure which will be around 13-14psia.

   Solar Boiler:
This boiler will be a cross flow closed heat exchanger where solar heated water at a temperature of 210 deg f will transfer energy to the low pressure condensate.  The condensate will flash to steam and pressures of around 10-12 psia will be generated.  By operating at these low tempratures and pressure the solar energy will provide the nergy needed for phase change of the condensate to steam.  Subsequent superheating will optimize efficiencies while still allowing for 75% of the cycles energy to be derived from low cost solar energy.

   Biomass Superheater:
This can consist of several styles of combustors, probably a simple grate style boiler will accommodate the widest range of fuels at smaller energy scales.  Unlike conevtnional boilers which require water waters and drums this boiler will simply be a couple sections of boiler tube heating elements arranged in the gas path in a crossflow pattern (inlet steam paired with outlet flue gas).  Exiting flue gas is ducted into the algae scrubber for cleanup.

   LP Steam Turbine:
To optimize efficiencies blading would need to be redesigned for this cycles low pressures.  However even without doing this a used LP from a retired conventional power plant would run on superheated low pressure steam with a total differential pressure of 10 psig.

Water Cycle
The water cycle consists of three main subsystems, the aquaculture pond, the algae scrubber, and the solar water heater collector.

Aquaculture Pond:
The aquaculture pond serves two main purposes, it provides cool water for the steam condenser while also producing warm or even potentially cold water fish.  A continual circulation of thermally disinfected solar discharge water aerates and helps control the biology of the system.  Additionally low cost algae protein provides a near zero cost symbiotic food input.

Algae Scrubber:
Condenser discharge at 110 deg F is at an optimal temperature for growing alage, this is promted through a managed algae raceway where circulation and water chemistry is optimized for low cost open algae production.  Algae growth is further enhanced by scrubbing the plants exiting warm 200 degree flue gas of CO2.  This acts as a dual energy recovery technique.  Thermal energy is captured in the raceway, while the CO2 enhances algae growth for greater bioenergy yields.  The algae can be pressed for liquid fuels, used as a feed source or simply composted as a CO2 sequestering and soil amendment strategy.

Open Solar Thermal Collection System:
To date concentrated solar power (CSP) has only been viable in the sunniest of regions, while organic rankine cycles (ORC) the other low temperature solar thermal option has proven to have too low of efficiencies to be commercially viable.  In an attempt at a solar breakthrough this cycle utilizes the best of both low temp systems and high temp systems. This is done through fuel source hybridization.  Solar energy is collected at low temperatures with water, under the premise that if this low cost solar energy can provide the bulk of the cycles energy (75%) by providing the heat of vaporization that the remainder (25%)can come from a high temp combustible source and raise overall efficiencies (400% not a typo).  This hybridization may provide cost breakthroughs.
In order for that to happen though the collector must take advantage of the lower temperature requirements through a very simple low cost design.  As crudely illustrated in the sketchup picture an open trough feedwater system may be able to achieve this breakthrough.  The system could consist of little more than a shallow trough pitched and dug in the earth then blacktopped over and covered with three layers of low profile greenhouse film.  Water would flow through these shallow troughs and become heated to 120-150 deg on most days.  A variation of this design would provide the final heating of water, here a deeper parabolic earth trough is constructed, the walls are lined with mylar (or other low cost comparable reflective) .  A mirror reflects the energy gathered in the walls onto the flowing stream of water below and raises temperatures to just below boiling point. System controls optimize flow through these heaters to maximize energy capture.  Excess production is stored in an insulated tank for night time and cloudy day reserves.

After water runs through the solar boiler it is pumped back to the aquaculture pond at a temperature of 90 deg F.  This water serves as continual supply of thermally disinfected water for the aquaculture system.

Though too complex to quickly calculate the proposed system promises greater efficiencies than operation of any of the subsystems separately.  Waste heat and flue gas from the electrical thermal cycle becomes a productive input into the other subsystems.  What needs to be determined is if this approach will enhance efficiencies and lower economic barriers significantly enough to begin to displace conventional fossil fuels.. Thoughts suggestions??


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