>>>>>> Assuming it can be made to work the yield from algae is claimed to be
>>>>>> 30,000 gallons diesel/acre-year. пїЅ This comes out to be 30 kW/acre
>>>>>> (24/7/52).
>
>>>>>> (This is over 3X the gross income as growing berries so it is
>>>>>> probably
>>>>>> economical especially considering the quality of the land doesn't
>>>>>> matter.)
>
>>>>>> Taken along with the 40%% efficiency of a diesel engine, the
>>>>>> mechanical
>>>>>> work from algae oil is only 12 kW/acre (24/7/52).
>
>>>>>> Dish Stirling averages over 120 kW/acre mechanical work (24/7/52).
>
>>>>>> Now, to be sure, no one will deny that liquid fuel is often a
>>>>>> convenient way to store and transport energy, but even if the
>>>>>> electrical energy storage device, i. e., battery, pumped water, etc.,
>>>>>> is only 10%% efficient, dish Stirling _still_ beats bio diesel in
>>>>>> mech.
>>>>>> energy/land use.
>
>>>>>> Bret Cahill
>
>>>>> Not a useful comparison Bret.
>
>>>> Land and capital cost of covering land are always important.
>
>>>>> But at least neither one actually works.
>
>>>> San Diego Gas & Electric just bought 40,000 Stirlings for the desert.
>>>> You might want to tip them off.
>
>>> The only thing I've heard about is conventional turbines running off
>>> solar thermal. Can you give a reference?
>
>>>> Diesel from algae seems likely.
>
>>> I don't know. Is it just 5-10 years away, like hot fusion?
>
>> This pretty much explains at least the current popularity of solar
>> thermal.
>
>>> This is
>>> 1950's sci-fi that has yet to materialize. Assume the tech; you've
>>> still got to get water to the desert.
>
>> Dish Stirling has a closed cooling system.
>
> Water for the algae,
The algae tanks are closed as well. They recycle the water. The only
process H2O required is that which will supply the H for the
hydrocarbon.
More oil is taken out of the operation than water in so the cost of
trucking water to a remote location is negligible.
Anyway it's a moot issue as there are aquaducts and wells in many
desert areas.
>>>>> Give me a functioning Stirling generator and I can charge up the
>>>>> electric car off the wast heat from heating and AC right there at my
>>>>> house.
>>>> That violates the 1st and 2nd law of thermodynamics.
>>> Huh?
>
>> The efficiency is too low at any rate.
>
> Not if it is a Stirling engine.
No real engine can beat the theoretical Carnot efficiency, 1 - Tc/Th,
which is just a restatement of the 1st + 2nd laws of thermo.
If Th = 100 C and Tc = 0 C then the Carnot limit is only 1 - 273/373
or 26%%.
The best prime mover Stirlings only get about half Carnot so you are
already down to 13%%.
And that's for a 180 F delta T.
I recently heard about a United Technologies geo thermal plant
powering a resort in Alaska. They probably have freezing cold water
available for the cooler but the hot ground water is only 160 F --
cooler than coffee.
It's a Rankine cycle binary system; they run the hot and cold water
streams through heat exchangers to evaporate and condense an organic
working fluid with a low boiling point. The organic vapor powers the
turbine.
The Carnot efficiency of that plant is only 1 - 492/620 = 21%%.
The Rankine cycle comes closer to Carnot than any other real engine
cycle but after losses in the heat exchangers, they probably don't
even make it out of single digits.
Of course, if the heat is "free" who cares? They probably use the
water leaving the evaporator to heat the place, CHP (combined heat &
power), and then inject it back into the ground a half mile away from
the production well.
Or, if the water is clean enough they could just use it for hot tap
water.
Lots of options if you have geo resources and money.
Bret Cahill
