Re: Hydrogen economy will never exist

From: william mook (william.mook_at_mokindustries.com)
Date: 07/07/04 

Date: 7 Jul 2004 04:26:46 -0700

"daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote in message news:<RSIGc.24045$iJ4.17634@twister.nyroc.rr.com>...
> "william mook" <william.mook@mokindustries.com> wrote in message
> news:407c5321.0407051848.3cfa570f@posting.google.com...
> > Since the junction temperature is below 100 C the heat is low-grade.
> > It is costly to collect, and useful as well in the right environment
> > as you suggest.
>
> Exactly. So the proponents of a 'solar plant on every roof', could have a
> unit in the back yard or where ever, and use the low grade heat to
> supplement home heating or hot-water costs. Even if only used part of the
> year, it might prove economically sound.

Depends on the cost of the heating unit. We have something a little
more complicated than a hot water heater, but not by much.

http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=APPL&pid=04233383000

Sears sells water heaters in the 30 to 50 gallon range in the range of
prices $250 to $300 - from what I could tell.

Water has a heat capacity of 4.184 Joules per degree C per gram. A
gallon contains 3,637 grams of water. So, a 40 gallon tank stores
608.6 kJ per degree C. A kWh contains 3,600 kJ. So, each degree
'stores' 0.169 kWh. Taking water from say 22 C to 82 C requires 8.45
kWh. To store heat in a hot water tank costs $250 - that's $29.50 per
kWh - about 1/4 the cost of a battery, but not cheap enough to really
write home about. Now, that's just for the tank and controls. It
doesn't include the heat exchanger cost at the concentrating PV and
the insulated connections and controls for that. So, costs can easily
double.

Like I said before, this makes a lot of sense to do in a place like
the South Pole where energy costs are $16 per gallon of Diesel fuel.
It makes less sense where energy costs are less.

Capturing the heat though is an interesting possibility and worth
considering. But we've always got to look at these technically
interesting things and how they impact cost and demand that for each
watt of power generation capacity and each watt-hour of energy storage
capacity that strict costs per watt and costs per watt-hour are met.

>
> Haven't run a lot of numbers for this, but if $0.30 gets one watt of
> electric and 3 watts of 75C heat, at 1200 hours operating a year, that may
> be about 400 hours a heating season. 1200 watt-hours of low-grade heat per
> heating season would be $0.30 / 4096 BTU Although that is over $7 per
> therm, I think some refined calculations would be in order. For an annual
> output of one therm during just a 400 sun-hour heating season, you would
> need about a 24.5 watt electric unit for a capital cost of $7.32. At 8%
> over 20 years, the capital cost of providing that therm just in the heating
> season would be $0.75. That is competitive with NG used to heat many homes
> in the NE/MW today. And that doesn't consider the electric produced.
> Obviously, including the cost of replaced electricity, the setup is even
> more attractive.
>
> A 4kWelectric unit could supply 163 therms a year for an avoided NG
> (@$0.75/therm) cost of ~$122/year. If the modifications needed to utilize
> this heat add $0.20/watt-electric ($800 for a 4kW unit), then the annual
> payments at 8% for 20 years would be $81.48. Maybe not enough to run right
> to the drawing board, but if NG prices continue to rise.....
>
> Hot water heating, with its year-round usage might be even better and
> represent a more realistic load for this level of thermal output. And
> appeal to a wider geographic audience.
>
> daestrom

Relevant Pages

  • Re: Hydrogen economy will never exist
    ... Depends on the cost of the heating unit. ... more complicated than a hot water heater, ... Water has a heat capacity of 4.184 Joules per degree C per gram. ... To store heat in a hot water tank costs $250 - that's $29.50 per ...
    (sci.energy.hydrogen)
  • Re: electricity savings
    ... buildings that actually use the heat generated by the fluorescent lights to heat the building. ... That seems rather unlikely given the differential costs in gas and electricity. ... The only way an electrically heated office will approach the economy of gas or oil fired heating would be via heat pumps, not lights! ...
    (uk.tech.digital-tv)
  • 80% vs 93% AFUE
    ... Only issue here is that we need either several deep wells or must dispose of the well water on the surface, thru sprinklers, into a newly dug leaky tank, or into the storm drainage ditch. ... In practice, because this new home will have 9 inch insulation in the walls and about 12 inches in the ceiling, will be surrounded by trees that BLOCK the late afternoon sun, the actual costs won't be much more than what I am paying now for 12 SEER. ... Heating costs for the new home will rise proportionally to floor space but again due to the extreme insulation, not as fast a rise as the increase in floor space represents ...
    (alt.home.repair)
  • Re: Solar breakthrough - when?
    ... > Also, the heat collector for this is pretty much free, so the only problem ... and how much it costs to build the warm/cold water heat ... The usual problem is the delta T's of the coupling heatsinks or ... to get under 0.3 degrees per watt. ...
    (sci.energy.hydrogen)
  • Re: A racial incident
    ... money and pay it back over time with cheaper money. ... I found out that due to our incoming water temperature ... during the winter the water would not heat up to our deisred 125F. ... considering my total costs I did a cost benefit analysis and ...
    (rec.boats)