14 ways solar power costs will decrease... sharply? really?

I think on balance he is on the right track. That said, the piece is so filled with typos it hurts his credibility.

Icarus

 

Looks reasonable to me. A lot of it is saying what we need to do, not what is going to happen. 'Sharply' is suitably vague. And I would say that they have already done so, about 50% over the last 10 years. See: Module Pricing | Solarbuzz

Americans use about 250 kWh / person / day (all energy uses). Solar PV produces around 2 Watts / meter^2. Do the math. No matter how you look at it, it is not a small task.

 

uh, your number are off by 2 orders of magnitude on the PV production. Our house of 4 uses 250-450 kWh/mo, so that number is way off too... but what does "all energy uses" really mean? Are they including transportation, etc?

 

I don't understand when you say "solar PV reduces 2 watt/meter(squared?)".

As I understand, on a clear day, the sun will provide ~1000 watts per meter squared (ideal insolation). PV solar panels under ideal conditions can harvest ~11 to 15% of that. Using realistic derating it comes ou perhaps 50 to 100 watts per square meter, multiplied by the number of hours of expected sun.

So please clarify.

Icarus

 

All energy uses includes everything. Transportation, heating, cooling, making stuff, etc. If you plan on replacing coal, oil and uranium, this is your goal (or combined with other source of energy and conservation).

2W / m^2 is not per m^2 of panel, but rather for ground coverage and includes thing like shading, support systems, maintenance, night time hours etc. If you are planning on replacing coal, oil, and uranium, etc. this is your land usage.

 

Many of the facts are legit, but the tone is rah rah. If solar cuts its costs in half over the next decade as predicted it will still be a tiny proportion of use in the united states. Germany has a feed in tarrif of over 0.30 euros /kwh and still only about 2% is solar. That goal of getting to 2% might be reasonable in the next 20 years, I doubt we will climb higher faster.

Please correct this figure, but I thnk eia has solar in the united states at 0.02% of electricity generation in 2009. I'm not sure about the math of 2w/m2 but 30% growth per year of something around 0.02% of electric generation is still small after a decade. Only high natural gas prices and problems with wind would get it to increase much faster.

 

I doubt anybody being reasonable expects solar to be the end-all and be-all for our energy needs. Natural gas can play a large part of transportation, as well as petroleum (but hopefully at levels a smallish fraction of current usage as it will not go down in price or environmental harm) and some electricity. Electricity is probably not the best method for heating houses in cold environments, wood pellets and natural gas makes sense there too. Wind is currently producing 10x the electricity of solar. Using kite-like wind turbines up in the levels where there's more consistent wind has a lot of promise. There's also geothermal, biomass/biofuels and hydroelectric.
11% of U.S. Energy Production from Renewable Resources in 2010 – CleanTechnica: Cleantech innovation news and views

Then that's not a fixed number, like Icarus used. Technology/process/construction improvements can increase that. Solar thermal can run for more hours per day as the energy is stored as heat, so that might change your number a fair bit right there. (Electricity can be produced largely when needed, not just when it's sunny, unlike photovoltaics).

 

Well, for starters, just increasing efficiency would cut the amount of coal, oil, uranium needed by a very large amount. Solar, esp solar thermal has the capacity to store excess for nighttime user pretty efficiently. Using CSP in addition to PV very much changes the equation. And the whole thing is a bit of a straw man, because there's no one solution. Just like there's no one fossil fuel that provides all of our energy needs. So saying we need to replace everything w/PV is absurd.

 

Certainly, I am not. Just trying to frame the debate.

Electricity is a fine way of heating houses, current COP on heat pumps are in the 3-4 range (that is 300%-400% efficiency (sort of)). Wood pellets are an energy intensive way of making wood palatable to city dwellers.

Nope. As anyone with a Prius knows, storing energy for use later (while helpful) always gets you less energy in the long run.

 

Not sure which figure you would like corrected.

30% growth from 0.02% (2009) gets us to 0.466% by 2021, 6.424% by 2031, and 100% sometime in 2041 (current, electricity only).

 

Uhm, you're talking about residential geothermal for the heat pump, right? Otherwise you can't get a COP like that. I wasn't really thinking about that, but it does make sense, providing you're not living in a dense area (needs a certain amount of ground per living area).

I haven't really studied them, but they have their strong proponents. Our school in northern MN used it decades ago, basically it was waste from nearby sawmills and paper plants. If you have the room for an outside high-efficiency wood furnace, that might be better for EROEI, but like you imply, requires a bit more physical effort and inconvenience. In either case, I don't expect wood to play a big part in heating. There's so much waste in construction though (30% of our landfills), that at least the wood from that should be used for something.

Depends on what you're measuring. While it will return less energy than when you had it first available, compared to starting up energy production again (turning the engine back on, or using a backup coal plant), then it may save you energy overall.
If you look at it as watts in vs. watts out, you're right. If you look at it as energy consumed vs. work done, then it's a different matter altogether. Hence the reason for a battery pack on the Prius, even though you get less energy out of it than you put into it.

I think PVs for homes and private businesses, solar thermal and kite-based wind for utilities, mix in some geothermal and existing hydroelectric and then we're getting somewhere.

 

Ground source heat pump, you mean? Unless you have a volcano nearby. But the technology exists to make air source heat pumps around that COP (even in cold climates).

Not sure I have ever seen one of those. Mostly wood furnaces are a chore, a wood stove is quaint.

Since we were talking giant brush strokes (and PV), yes I was talking watts out.

I just want to get people starting to think about the size of these things they are tossing about.

Wind: 1 to 2 W / m^2 Total available: 43 kWh / person / day
Offshore Wind: 3 W / m^2 Total available: 4.8 kWh / person /day
Geothermal: Total available: 8 kWh / person /day
Hydro: 0.5 W/m^2(?) Total available: 7.2 kWh / person / day (twice current)

That leaves 187 kWh / person / day (out of the 250) for solar (PV, concentrated PV or Thermal) or conservation.

[Yes these are all guesstimates. See: http://www.withouthotair.com/]

 

Which number of Icarus's did you think was fixed? 1000W/m^2 is pretty much a definition. Real world numbers will vary wildly.

 

Molten salts are an incredibly efficient way to store/release heat. well over 90% efficient, so it's a pretty good mechanism. Burning coal is really inefficient. You're comparing inputs to outputs.

 

Huh? For 2W/m^2 for solar: the claim was made that "[thermal storage] might change your number a fair bit right there." It would change them by -10%, which I didn't take as 'a fair bit', nor in the direction that seemed to be implied.

 

The number that seems off is the 0.02% from solar in 2009. I am hoping someone has a 2011 number. I'm sure it is still well bellow 1%.

As with all trends I would expect an acceleration than deceleration. I really doubt we will get to 2% solar by 2030 without a substantial feed through tariff or other mandates/incentives.

 

Wood pellets are still made from sawmill waste (mostly). I have a wood pellet stove in my downstairs, that I'll run during the winter. It drastically cust my oil usage, and it's not tapped into the duct work at all. Naturally, heat rises, and I keep my HVAC fan turned on 24/7, so it also helps to circulate that air through the house. Last winter (2009-2010) I used 1 tank of heating oil with about 1.5 tons of wood pellets. This past winter, I had issues with my liner getting clogged, and had to shut down the pellet stove until I could get it fixed properly. I've used almost the same amount of heating oil again this year. They can help, but it's still a limited resource if you use the waste to produce the pellets. I refuse to use corn (I can use a 50/50 mix) because to me corn is food and should be used as such. A bit OT, I know, but since I've got a pellet stove, figured I would chime in. Be glad to answer what I can for those with questions.

 

Forgive me my foibles, but "hot air rises". I know, it works in this instance, and it is what you meant, but I fight that imprecision every day, where people think it applies to other kinds of heat transfer.

Sounds like you might be running it bit closed down (not enough air). Is it thermostatically controlled?

And it isn't really 'waste', that is it wouldn't go to a landfill if they didn't make pellets from it, it would be used for some other wood product.

 

I would argue, that while wood stoves are certainly not a solution for most, they are not "quaint". Modern EPA rated stoves bur very clean, and very efficiently. I heat my house, shop and my wife's studio with wood nearly 100%. We buy mill ends from a local sawmill by the truck load. The are Kiln dried, stored inside, burn very clean,, and they are very cost effective. A 5 cord load cost me ~$300 and will last us 2 years in the Pacific N.W. I also burn lumber scraps from my construction projects as well as slash from land clearing when I can get it free, with very short haul. All wood fibre that would other wise go to waste.

Our stove heats the entire house no matter how cold, and the heat is incredibly even throughout the house. We have a fan at the top of the stairs that directs air to the back corner of the house.

A solution for AGW, not really, A solution for those that live in urban areas? not really, but it is a very real solution for some. I have read that burning wood is essentially carbon neutral. Burning what is in essence wood waste can only be a good thing instead of having it burned in slash piles or tepee burners.

As for heat pumps,, the other very efficient heat pump system is a hot water capture heat pump, if you live in a climate where A/C is used more than heating. By capturing the waste heat from the heat pump into hot water, you get "free" hot water, and the A/C unit runs more efficiently.

Icarus

PS I am also still unclear as to the 2 watts per meter/square, is that on a daily basis, hourly or yearly? I can tell you, we live off grid 6 months a year in a remote location with PV solar. Our array is quite small, but in ~ 36 sq/ft we get ~ 300 watts, for about a 4 hour average over the course of the day. For simple calcs that I use for clients is about 10 sq/ft of PV per 100 watts is a pretty good rule of thumb.