DarthPuppy
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Re: North America's largest coal power plant to become 44-MW solar farm

Fri Mar 18, 2016 8:46 pm

Thank you GRA and RegGuheert for addressing the aspects of the relative efficiency/economics of wind, hydro and solar options for the different areas. That is something I can't speak to as I've only looked closely at solar as I can't realistically install my own hydro or wind solution under So. Cal's regulatory scheme. :cry: I would love to have installed wind in addition to my solar panels.

So if solar is more economical than other options, even that far north, I can understand Canada's choices. I'm just skeptical if that is optimal for global green objectives, hence my questioning the efficiency. Over the last decade, solar production has grown substantially and costs have come down, because of the amount of investment made and the political willingness to support deployment and overcome barriers. If the same investment and political will was applied to wind and hydro and other green options, I would think those would be more competitive too. So I'm inclined to think that from a global perspective, the northern locations would be thinking more strategically if they allocated toward those other options and left precious solar resources for use by more southern locales.
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RegGuheert
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Re: North America's largest coal power plant to become 44-MW solar farm

Sat Mar 19, 2016 3:33 am

DarthPuppy wrote:The impact of geographic location on solar panel output is well studied and documented.

And studies showing that during the summer with day-round sunlight they can produce well ignores the flip side of the year where they produce very little.
Anyone who reads this forum knows that I am a very big proponent of photovoltaics. That said, I will say the problems of effectively applying photovoltaics gets doubly harder as you move toward the poles: wintertime PV production drops while wintertime loads increase. Even at my location near Washington, DC, this makes running a typical home from solar power a significant challenge. Here are two examples:

Photovoltaics with net metering on my own home (39 degrees North latitude): Electricity production in December and January is approximately 1/2 that of June and July. But electricity consumption in January and February is often 3X what I use in June and July due to the operation of a heat pump space heater. With the magic of net metering, I am able to size my photovoltaic system at 2X the summertime load in order to meet the total load of over 18 MWh/year. With that arrangement, I bank over 3 MWh during the summer months to be consumed during the wintertime. Since storage of that much electricity is not practical with current battery technology, I would need to triple the size if the PV array in order to operate the heat pump in the wintertime in an off-grid condition. My roof MAY be able to accommodate this much PV with current technology, but that would represent a significant waste, IMO.

An entirely off-grid home nearby (same 39 degrees North latitude): This home is about the same size as mine and was designed from the ground up to be very thermally energy efficient and to store significant amounts of thermal energy in the concrete and stone slab in the basement (with R40 insulation below the slab). This home has both a PV array for electricity and a solar thermal array for heating both water and the basement slab. The photovoltaic array is about 1/3 the size of the array on my home and produces about 1/10 as much electricity as my system due to being battery-backed rather than grid-tied. The thermal array is 2/3 the area of the PV array, but it is 4X to 5X as efficient. Both arrays are mounted at steep angles to optimize wintertime production (and reduce summertime production). Both the electrical and the thermal systems are backed up with fossil-fuel-based systems. Home comfort is maintained in wintertime using a Swedish fireplace in the center of the home. Without it, temperatures get down to about 45 degree Fahrenheit in the worst weather conditions (with all systems functioning properly).

As you move toward the poles, both of these homes would require both larger systems AND better insulation. Annual solar production would drop (even though summertime production may increase). As you approach the Arctic Circle, the ability to provide either electricity OR heat from the sun in wintertime would approach zero. This is why countries such as Germany are pursuing using hydrogen for long-term storage of energy. Unfortunately, hydrogen storage increases the amount of electricity needed by 2X or 3X due to the significant losses. OTOH, the *theoretical* efficiency of electrolysis is 120%, meaning that in the future you may be able to consume heat during electrolysis in summertime. Likewise the theoretical efficiency of recombining hydrogen and oxygen is only 83%, meaning you WILL get heat from the fuel cell. Since you need heat in the wintertime, it can be a beneficial arrangement if the heat can be used. But we are not very close to these theoretical efficiencies today, so you get waste heat in both reactions.
DarthPuppy wrote:If I am correct on that point, then I'm correct regarding the resource allocation efficiency aspect, at least until such time as we are no longer resource constrained regarding solar panels and we can cheaply deploy them everywhere we desire power. I hope we get there sooner than later. Production is growing and costs are dropping, but we have a long ways to go yet.
Agreed. But I am hopeful that some day most of our needs can be met with solar power that is either used directly or stored thermally, in batteries or in something such as hydrogen. Today, I am in favor of preferring photovoltaics where they can be reasonably applied, even in places such as Canada and Germany, since they have long life and very low maintenance and environmental impact when compared with wind. This is particularly true when PV is placed on rooftops. Unfortunately, when utilities get involved, PV starts to have significant land-use impacts.

Germany is currently doing significant damage to their environment by leveling forests and building wind generators. Fortunately there is significant opposition rising from the citizens there to this type of destruction. My preference would be to use a much more measured approach which would allow the preservation of our environment while solar and other technologies mature. I am intrigued by kite-based wind generators since they do not have the land impact of either wind turbines or utility-scale photovoltaics.
RegGuheert
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GRA
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Re: North America's largest coal power plant to become 44-MW solar farm

Sat Mar 19, 2016 2:38 pm

RegGuheert wrote:<snippagio>
As you move toward the poles, both of these homes would require both larger systems AND better insulation. Annual solar production would drop (even though summertime production may increase). As you approach the Arctic Circle, the ability to provide either electricity OR heat from the sun in wintertime would approach zero.
In general, for off-grid towards either pole you've got to go with a hybrid system, PV/wind, maybe hydro, plus often generator backup. I have a vague memory of spec'ing an off-grid home in Alaska once, and it had to be PV/wind. Hydro wasn't a very good option, as they had plenty of sun in the summer, and when they didn't the river was frozen. Given the choice between PV and hydro I'd always opt for PV, unless the electricity needs were very large, which was rare in the typical off-grid home. Closer to the equator, you've usually got more options. OTOH, there was this one site I spec'd which had terrible PV/wind options but great hydro potential - as described to me over the phone, if was at 5,000 feet in a rain forest on the side of a Mexican volcano, but had a stream with decent flow and incredible head, so hydro was the el cheapo (and really the only) choice.
RegGuheert wrote:<snip>
I am intrigued by kite-based wind generators since they do not have the land impact of either wind turbines or utility-scale photovoltaics.
Kite- or balloon-based wind turbine proposals seem to come around about every 10-15 years. The theory is wonderful, but the practical/safety concerns have always made it a non-starter in the past. Maybe the development of software and control systems for autonomous vehicles plus wireless power transmission over several thousand foot distances will lower the price/weight of same to the point that kite-based systems won't require the large land safety clearances under and around them that they currently require (after all, if the wind stops or their tether/power transmission cables break you have to make sure they return to earth gently, without falling on people or their homes/businesses). You also need to make sure that the tethers don't get tangled.

Even dropping a typical short extension cord from a height of several hundred to several thousand feet could injure or maybe even kill someone it hit; dropping part of a much larger and heavier transmission/tether on someone from the same height would probably remove all doubt as to fatality. And if you're talking about putting the generator aloft instead of on the ground, you might as well drop an inert bomb on someone. Tethered aerostats used to hoist radars aloft occasionally break free, and kite or balloon-based turbines would be multiplying the numbers aloft by many times:
NORAD: Runaway military blimp secured in Pennsylvania
http://www.wbaltv.com/news/jlens-blimp- ... n/36097348
. . .Officials said the break occurred around 12:20 p.m. at Aberdeen Proving Ground. NORAD officials told WBAL-TV 11 News reporter Kim Dacey around 3:15 p.m. that the blimp was secured in an unpopulated area of Moreland Township, Pennsylvania, about 150 miles from Aberdeen. . . .

Authorities in the Bloomsburg area reported the tether cable from the blimp took down power lines. Power outages were reported in the area, and Bloomsburg University canceled classes as a result of power outages on the campus.

Now just imagine the risk factor of hundreds or thousands of tethered aloft turbines instead of a couple dozen. I've got to wonder how many people were killed or injured by falling barrage balloon tethers in WW2, even though those were typically only sent aloft when an air raid warning was issued (in civilian-populated areas; military areas might have them up a lot more), and people would be spending time when the balloons were aloft in bomb shelters. I do see that Title 32 CFR 536:26 allows for claims during war by foreign civilians (at least in foreign countries) suffering damage to property/injury or death due to the operation of barrage balloons among other things: https://books.google.com/books?id=3RazA ... es&f=false

See page 134, near the bottom of the left column.
Last edited by GRA on Sun Mar 20, 2016 4:01 pm, edited 1 time in total.
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].

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RegGuheert
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Re: North America's largest coal power plant to become 44-MW solar farm

Sat Mar 19, 2016 4:11 pm

GRA wrote:Maybe the development of software and control systems for autonomous vehicles plus wireless power transmission over several thousand foot distances will lower the price/weight of same to the point that kite-based systems won't require the large land safety clearances under and around them that they currently require (after all, if the wind stops or their tether/power transmission cables break you have to make sure they return to earth gently, without falling on people or their homes/businesses).
All generation is done on the ground. The kite pulls cables out and that turns a generator. Once the cable is all pulled out, the kite is furled and pulled in and then the cycle repeats itself. The kite and its support cables are all that fly.

Here is a link to a system which I have previously read more extensively about. I think you will find more information there.
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

GRA
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Re: North America's largest coal power plant to become 44-MW solar farm

Sun Mar 20, 2016 3:40 pm

RegGuheert wrote:
GRA wrote:Maybe the development of software and control systems for autonomous vehicles plus wireless power transmission over several thousand foot distances will lower the price/weight of same to the point that kite-based systems won't require the large land safety clearances under and around them that they currently require (after all, if the wind stops or their tether/power transmission cables break you have to make sure they return to earth gently, without falling on people or their homes/businesses).
All generation is done on the ground. The kite pulls cables out and that turns a generator. Once the cable is all pulled out, the kite is furled and pulled in and then the cycle repeats itself. The kite and its support cables are all that fly.

Here is a link to a system which I have previously read more extensively about. I think you will find more information there.
Thanks, I'll check it out. Ground-based generators do reduce the weight up high, and I've always favored them for that reason. OTOH, frequent reeling in and out (plus the mechanisms to frequently furl/unfurl) also adds to costs and maintenance, and ISTM is likely to increase the likelihood of tether failures. I'd love to see somebody make it work commercially.
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].

The 'best' is the enemy of 'good enough'. Copper shot, not Silver bullets.

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