And who said solar thermal is dead?

[Grisu]

One cord of seasoned red oak weighs about 3300 lbs and has about 6050 btu's/lb of available energy in a wood gasification boiler. 3300 x 6050 / 3414 = 5850 kwh of available energy content per year on a sustainable basis on one acre of land.

My 6500 kwh solar system covers 400 square feet of land and has average annual production of 9000 kwh. One acre of land has 43,560 square feet, divided by 400 = 109 solar systems like mine, or 109 * 9000 = 981,000 kwh of energy, 168 times the energy potential of that same land growing trees.

Looked at differently, 1 cord of css seasoned red oak sells for about $225 in my area. 981,000 kwh at the retail rate charged by my utility sells for $105,948.

Another different look. 9000 kwh at my retail rate = $972 with $0 labor cost and 0 risk of physical energy or death from cutting down several trees and css for retail sale.

And yet one more different look. My solar system cost $30,000 before any tax credits, incentives. For growing and processing wood: cost of one acre of land: $_____; equipment to process wood: chainsaw, chains, chaps, helmet, gloves, and boots: $_____; splitter: $_____; tractor/equipment to haul the wood out: $_____; value of time invested: $_____; replacement and maintenance costs: $_____; add your extras: $_____.

Based on these numbers, one acre of land for solar electric produces 168x the usable energy per acre than using land to grow trees for energy.

A more elegant way of looking at the numbers. And yes, I was not looking at sustainably harvested wood just to show how outlandish that initial "thinking" was. Let us also not forget that Ivanpah is located in the Mojave desert. You won't grow that much biomass there without massive irrigation.

 

[ihookem]

OK, I stand corrected. I still think it is darn ugly , and I'm not ripping anyone, but all these liberals ( not saying any posters are ) but we get these people in the biggest hissy fit anytime a northern spotted owl , or the long nosed teat mouse, or the desert turtle on the Bundy farm, or the Gile trout in New Mexico, we cant even put cows there, and some of it is completely closed for much of anything for recreation. Why is this ok? So Las Vegas can has lights on 24/7? Or Las Angeles can too? Still ugly and if there was any recreation value there, or anything scenic it is now off limits. 5.4 Sq. mi. is a lot of space and it's not green space anymore neither. If there is that much sun there let the residents and companies put their own solar on their walls and roofs.

 

[begreen]

This is desert land, not farming land. The reflectors look to be about 10 ft above the land which should allow for grazing animals or critters looking for shade in the desert one would think. However, they are investigating bird kill numbers. For comparison, so far they match about what my neighbor reports his big plate glass windows kill per month during migration season. And that is only one house.

 

[Grisu]

OK, I stand corrected. I still think it is darn ugly , and I'm not ripping anyone, but all these liberals ( not saying any posters are ) but we get these people in the biggest hissy fit anytime a northern spotted owl , or the long nosed teat mouse, or the desert turtle on the Bundy farm, or the Gile trout in New Mexico, we cant even put cows there, and some of it is completely closed for much of anything for recreation. Why is this ok? So Las Vegas can has lights on 24/7? Or Las Angeles can too? Still ugly and if there was any recreation value there, or anything scenic it is now off limits. 5.4 Sq. mi. is a lot of space and it's not green space anymore neither. If there is that much sun there let the residents and companies put their own solar on their walls and roofs.

Please tell me which of these options look aesthetically more appealing:

coal power plant: http://i2.wp.com/www.greenoptimisti.../07/Coal-Fired-Power-Plant.jpg?resize=300,161
coal mining mountaintop removal: http://www.washtenawvoice.com/wp-content/uploads/2009/10/images_1013/mountain-top.jpg
Alberta tar sand removal: (broken link removed)
Dakota fracked oil wells: (broken link removed to http://ecowatch.com/wp-content/uploads/2013/01/aerialFracking.jpg)
Uranium mining (Australia): http://www.acfonline.org.au/sites/d...australia-nuclear-uranium-mining-ranger_0.jpg
Hydroelectric dam: (broken link removed to http://peakwater.org/wp-content/uploads/2010/11/hydropower1-300x241.jpg)
German Windfarm: (broken link removed to http://images.nationalgeographic.com/wpf/media-live/photos/000/180/cache/energy-frozen-fish-wind-farms-turbines_18081_990x742.jpg)

In the end, we all want the cheap labor that those energy sources provide. As long as we value that more than the biosphere we live in, we will keep building such "monstrosities".

 

[sesmith]

One cord of seasoned red oak weighs about 3300 lbs and has about 6050 btu's/lb of available energy in a wood gasification boiler. 3300 x 6050 / 3414 = 5850 kwh of available energy content per year on a sustainable basis on one acre of land.

My 6500 kwh solar system covers 400 square feet of land and has average annual production of 9000 kwh. One acre of land has 43,560 square feet, divided by 400 = 109 solar systems like mine, or 109 * 9000 = 981,000 kwh of energy, 168 times the energy potential of that same land growing trees.

Looked at differently, 1 cord of css seasoned red oak sells for about $225 in my area. 981,000 kwh at the retail rate charged by my utility sells for $105,948.

Another different look. 9000 kwh at my retail rate = $972 with $0 labor cost and 0 risk of physical energy or death from cutting down several trees and css for retail sale.

And yet one more different look. My solar system cost $30,000 before any tax credits, incentives. For growing and processing wood: cost of one acre of land: $_____; equipment to process wood: chainsaw, chains, chaps, helmet, gloves, and boots: $_____; splitter: $_____; tractor/equipment to haul the wood out: $_____; value of time invested: $_____; replacement and maintenance costs: $_____; add your extras: $_____.

Based on these numbers, one acre of land for solar electric produces 168x the usable energy per acre than using land to grow trees for energy.

Your numbers look convincing until you realize the amount of energy that is needed to heat a house in the northeast. Except in a very tight modern, small house, solar pv is an expensive choice to use for heat.

Take my old farmhouse as an example. When we heated it with an oil forced air furnace, it took about 800 gallons of oil to do that. Convert that 800 gallons burned in a 78% efficient furnace into electric resistance heat, and you're looking at about 25360 kwh of electricity. Divide that by the 9000 kwh per year your 30k system produces and you would need about an $84500 system to supply that much electricity per year. This would save approx $3200 / yr in oil at $4 per gallon and take about 26 years to pay back the solar cost with fuel savings.

When we heated our home with wood, we used approx 6.5 full cords of wood (which I cut myself). However, if I bought that wood at $200 per cord it would cost $1300 to heat the house, saving $1900 per year with no outlay of cash.

When I no longer was able to cut wood, we decided to put in a ground source heat pump. Some would say that a ground source heat pump is excessively expensive. The heat pump was 24k before incentives. The initial calculations I had, was that the system would cost me $647 per year to heat at $0.12 kwh electricity. FWIW, it has yet to cost us that much to heat with it (even after last winter), but at $647 per year, that is a $2553 savings over oil. That equates to a 9.4 year payback before incentives (6.6 years with the federal incentive).

So while it's easy to say that solar pv can produce more energy per acre than wood, that's not the whole story. 6-10 acres of wood will sustainably heat my house with no financial outlay (other than the land), and will take some carbon out of the air as well. Less than a third of an acre of my back yard will accomplish the same heating of my house (with the heat pump) at a greater cost, and more of a carbon impact (though I do buy my electricity as wind power, FWIW). It would take a very large solar array to accomplish the same, though it would use less acreage than the 6-10 acres of woods that would be required to heat with wood.

As far as Ivanpah goes, that's a different animal, and a very efficient use of land. In the desert, there's no real biomass to compare with either.

 

[jebatty]

For assumed equivalent btu need, your ground source heat pump produces about 5x the btu/kwh as resistance heating, for a COP of about 5, extremely good. I wasn't aware that such high COP units were available. Now, what about using solar for the electric needs for heat pump? Carbon neutral for home heating is a good goal to achieve.

 

[woodgeek]

Yeah. COP=5 is not commercially available in geos, when pump power is taken into account. Typical values are 3-4 in the field. ASHPs run 2-3 these days, but prob on the lower end in central NY.

Merely beating oil to calculate payback is not that useful. A hutch of rabbits eating organic microgreens can make BTUs cheaper than an oil boiler.

Nowadays, PV+ASHP is usually the best net present value, NPV, for a low-carbon heating system. Your geo incentive is what changed that equation.

 

[sesmith]

COP not 5. It was predicted to be on average to be 3.9 by the installer. Any time I've measured it, I've found it to be around 4 or a little over, so the predicted average should be pretty close. The mistake in my math is due to the fact that our old oil furnace was probably not anywhere near 78% efficient, especially with the old leaky duct work that we replaced when we put the new system in. I pulled the 78% out of the NREL heatcalc spreadsheet (default).

Agreed that if house construction is open enough and a central system is not needed, that mini split heat pump plus solar with incentives (especially as prices per watt drop) might make the most sense. Unfortunately, with my house design, as with many existing houses, life without a central system is not an option (if we want to be warm, at least). We survived quite a few years using a wood stove primarily for heat, but that didn't mean it was always that comfortable. With the heat pump, all rooms are within about a degree of each other and always at the tstat set point...how boring. I'm now spoiled.

My only point was to say that to extrapolate pv production of a panel out to say that pv makes more energy sense than biomass (my interpretation), ignores economics. Many people who heat with wood out in the country (myself included for many years) do so because it is the most affordable way to heat. Solar PV (in my estimation) only makes sense on a homeowner basis after everything else has been done and the home's energy use is brought way down. Once it's insulated, sealed, heated with some form of heat pump, etc, then the argument for pv makes much more sense.

I really am a solar advocate where it makes sense. I do think moving the grid toward renewables can be done and has to be done because that's where the majority of homes and businesses will continue to get most of their power from. The Ivanpah project is really cool, and I hope it helps prove that solar can be done on a large scale for a cost that is reasonable compared with business as usual, when all the costs of our energy are considered.

 

[woodgeek]

All very sensible, sesmith.

Ducted ASHPs with variable speed, inverter driven compressors are now available ("greenspeed"), should get Seasonal average COP close to that of a mini, like 2.5 or 3, in many climates, with central distribution.

The conventional wisdom about PV is a moving target...the old bit about doing everything else before PV is falling apart. The case has been made that passive house levels of insulation are not optimal, because about half that level of insulation (still 2-3x better than current best codes) with PV paid for with the savings on insulation results in a home that uses less energy than the passive house or is net zero.

Of course, if country folks find wood burning preferable, so be it.

 

[sesmith]

All very sensible, sesmith.

Ducted ASHPs with variable speed, inverter driven compressors are now available ("greenspeed"), should get Seasonal average COP close to that of a mini, like 2.5 or 3, in many climates, with central distribution.
.

Good to know. I'm patiently waiting for the variable technology in the minisplits to hit the hit the standard air source split units and become common place. We recently bought a house in South Carolina to retire to in a few years, and are renting it out in the mean time. It has an older 10 seer split system sporting many new parts (air handler, outside coil and compressor) so no need to replace it yet. But when the time comes, I'm sure it will be a new variable speed compressor unit. (No, we won't be investing in a geo system down there

 

[Dune]

Did anyone ever think of the 5.4 square miles ofland it takes up???? Ya could grow grass, cut it, and burn it in a furnace to make the electricity and come out ahead. ( I think) I think that is uglier than any wind mill farm. At least on windmill farms the deer and animals can go about and the farmers can still hay the fields right under the windmills. I don't think you can do anything with this land now.

Only if that was what was already going on there and is now displaced and no, you are totally incorrect. The efficiency of direct conversion of light into heat far surpasses the cost of the fertilizer alone, never mind the fuel used to harvest and transport. Sorry, not even close.

Out of curiosity, why are you opposed to clean renewable energy?

 

[Dune]

Your numbers look convincing until you realize the amount of energy that is needed to heat a house in the northeast. Except in a very tight modern, small house, solar pv is an expensive choice to use for heat.

Take my old farmhouse as an example. When we heated it with an oil forced air furnace, it took about 800 gallons of oil to do that. Convert that 800 gallons burned in a 78% efficient furnace into electric resistance heat, and you're looking at about 25360 kwh of electricity. Divide that by the 9000 kwh per year your 30k system produces and you would need about an $84500 system to supply that much electricity per year. This would save approx $3200 / yr in oil at $4 per gallon and take about 26 years to pay back the solar cost with fuel savings.

When we heated our home with wood, we used approx 6.5 full cords of wood (which I cut myself). However, if I bought that wood at $200 per cord it would cost $1300 to heat the house, saving $1900 per year with no outlay of cash.

When I no longer was able to cut wood, we decided to put in a ground source heat pump. Some would say that a ground source heat pump is excessively expensive. The heat pump was 24k before incentives. The initial calculations I had, was that the system would cost me $647 per year to heat at $0.12 kwh electricity. FWIW, it has yet to cost us that much to heat with it (even after last winter), but at $647 per year, that is a $2553 savings over oil. That equates to a 9.4 year payback before incentives (6.6 years with the federal incentive).

So while it's easy to say that solar pv can produce more energy per acre than wood, that's not the whole story. 6-10 acres of wood will sustainably heat my house with no financial outlay (other than the land), and will take some carbon out of the air as well. Less than a third of an acre of my back yard will accomplish the same heating of my house (with the heat pump) at a greater cost, and more of a carbon impact (though I do buy my electricity as wind power, FWIW). It would take a very large solar array to accomplish the same, though it would use less acreage than the 6-10 acres of woods that would be required to heat with wood.

As far as Ivanpah goes, that's a different animal, and a very efficient use of land. In the desert, there's no real biomass to compare with either.

Yet none of this disproves Jebatty's math. When did we decide to discuss resistance heating with photovoltaic?

If you want to talk ideals you should have torn down your old farmhouse and built a super insulated passive solar heated house and had no heating cost at all.
0 cost x 1000 (projected lifespan of house based on houses still standing in Europe and taking into account more modern building materials). Now that is some savings worth talking about.

 

[Dune]

and we paid for it? wouldn't be there if we didn't and continue to subsidize it each month.

Nor would Nuclear, coal or oil, all of which are heavily subsidised. You do realize that right?

 

[Doug MacIVER]

learning curve? enough gas to light how many homes, still a net gain, I guess.(broken link removed to http://www.kcet.org/news/rewire/solar/concentrating-solar/ivanpah-solar-plant-owners-want-to-burn-a-lot-more-natural-gas.html). maybe storage solution needed to make this work better? here is kcet link on all their ivanpah stuff (broken link removed to http://www.kcet.org/news/rewire/solar/concentrating-solar/)

 

[CaptSpiff]

(broken link removed to http://www.kcet.org/news/rewire/solar/concentrating-solar/ivanpah-solar-plant-owners-want-to-burn-a-lot-more-natural-gas.html).

Wow, I'm grinning ear to ear reading this.

Steam Turbine operators work diligently to make sure no water droplets enter the turbine with the super heated steam, then condense it back to liquid after the turbine to reheat it into steam again. I just assumed that they used a few hours of morning sun to reheat the boiler, and then they'd be good. Now the details come out that they burn Nat Gas all night long to keep the boiler water hot for a quick morning start.

Is that so they can claim greater daily solar production levels?

These guys have great futures in the used car business.

 

[woodgeek]

Seem cost effective to use the turbine/genny/grid connection 100% of the time rather than 25% of the time. Provided the nat gas rate makes the kWh cost effective.

 

[CaptSpiff]

Seem cost effective to use the turbine/genny/grid connection 100% of the time rather than 25% of the time. Provided the nat gas rate makes the kWh cost effective.

That would be great in concept, but I don't read it that way in the KCET article. Looks like they simply under estimated the bas burn needs to keep the water hot during "solar lows".

 

[woodgeek]

Sure, sounds like a significant design problem.....too high parasitic losses, or efficiency losses at low feed water temps. They can either fix the plant, which takes time and money (they might not have) or change their operating procedures to compensate, perhaps indefinitely.

For those keeping score, solar thermal still looks pretty dead.

 

[Doug MacIVER]

report on fox that ivanpah coming back for another 500Mil can't find anyother links, producing 1/2 the power promised. oh. moneywell? ps @7:12pm only link I could find

 

[Doug MacIVER]

updated kcet link (broken link removed to http://www.kcet.org/news/redefine/rewire/solar/concentrating-solar/)

 

[woodgeek]

Sounds like they are having some unit downtime...hardly surprising in such a complicated plumbing system. If it get's shaken out in a couple years, great. If not, its a lemon.

Too soon to tell.

 

[Doug MacIVER]

Sounds like they are having some unit downtime...hardly surprising in such a complicated plumbing system. If it get's shaken out in a couple years, great. If not, its a lemon.

Too soon to tell.

don't smaller protos usually proof out the larger ones, not in this case.

 

[woodgeek]

Not if the prototypes were made by a different entity, using different parts and materials.

 

[Doug MacIVER]

Not if the prototypes were made by a different entity, using different parts and materials.

from one design group, one engineering group, back by many investors. what you are telling me that proto wasn't produced by the final engineers and builder? not a start to finish deal? using different specs. I don't know but that is what your statement says to me.

 

[woodgeek]

A lot of this stuff doesn't scale trivially. You can build a heliostat and see that it works, but you don't know how much light it will deliver to your receiver when its a half mile away (without help from a computer model), you've got a high temp receiver on a tower, whose efficiency will depend on final operating temp, wind (and this height) and input power in a non-trivial way.

Y'know I'm not really a fan of this technology, I think it will get creamed by PV+grid battery technology and be a white elephant even if they get it working as hoped.

I'm just saying that a lot of things you can't simply build a smaller scale prototype, work out all the kinks and then scale up. Can you do that for nuke plants? At some level, you test everything you can test in a prototype (like material compatibility), and there is still engineering risk when you scale up. And my previous point was that while there have been other CSP plants at that scale that might be 'prototypes', if they used other configurations, materials, etc, then the risk remains.