Ok friends, I need your help. I’m trying to form an intelligent point of view on something that’s been bugging me for some time. The topic is the feasibility of small scale grid connected solar or wind.
Yesterday Diane and I went two Bread and Puppet up in Glover. In one of the political skits, the characters were making fun of ‘industrial power’ like our own Green Mountain Power… And we’re making the point that they supported small local power from solar and wind. I’ve often heard my friends talk that way..but as a scientist.. I’m not so sure I agree. While I could not be more committed to reducing our dependency on fossil fuels… I am not sure i get the economics nor the ecological sense of small scale installations.. On one hand, I love the consciousness raising aspect of seeing more small scale solar panels or wind generators behind folks houses.. But I can’t help thinking until we have a) closed loop metering (aka smart grid) which allows us to adjust generation to instantaneous load and/or b) low cost high capacity energy storage It seems that small scale solar is only feasible because we artificially give financial incentives… And those incentives are probably going disproportionately to middle class or above folks that might not need the break.. I also wonder about the cradle to grave environmental cost (say in carbon ) of manufacturing these complex panel assemblies for such low scale generation. My instinct tells me that what would really make this feasible is simplicity and scale.. That means larger scale fixed position solar installations or larger wind farms .. I know there’s a not-in-my-back-yard aspect to this.. But I think any energy generation change we make is going have pros and cons and will have to come with compromises.
So here’s where I need folks help.. Help me understand if I’m wrong in my thinking.. I may well be.. For example, my good friend gary reasoned that if enough folks got small grid connected solar that even without closed loop metering, the overall average energy load on the grid would decrease which would allow the generation to be reduced somewhat… Though the savings would be limited unless you could predict weather well enough at all the generation points to account for variations in sun or wind..
How can I get a handle on the economics of all this..? Opinions are fine, but i am looking for data and the math to support it . I want to be the best advocate i can for alternative energy…and want to have a well reasoned, fact based opinion. Any pointers most appreciated. !
Nite all, nite Sam
-Jc
– Posted using BlogPress from my iPad
hi John!
Not sure how much of this you may have seen or will find helpful, but just in case-
My parents have one of the trackers in their yard Williston near Lake Iroquois, and you can access all of the production data by month and by year: http://www.allearthrenewables.com/energy-production-report/detail/159 (The map they have on the front page of the site is interesting as well.)
It definitely shows the susceptibility to weather in this region in particular- the fluctuations are pretty severe.
I imagine the company keeps the data in a much more useful format for analysis- it would be really cool to see what changes the main grid experiences with the increasing density of the trackers around here.
hope you’re well!
dylan
Hey John,
Interesting points. A couple more that you could consider is that as a benefit on the small scale side, say everyone has a panel on their roof that is tied into the grid, this would allow a very wide surface area over which energy production is possible. This means that on a partly cloudy day, only half of the houses may be putting out full power at any given time, but would average 50% output for the day as the clouds go by, On the contrary, if a lot of solar panels were grouped together, such as on a solar farm, for part of the day they would be cranking out power while the sun was hitting the field, but when a small cloud rolled in, the power output would drop and the grid could fall short.
On the other side of the fence, you would have to look at efficiency of solar conversion. On a single home, what is the power input from the sun vs the power output onto the grid? What is the efficiency of a small scale inverter? What is the efficiency and cost differential between say a 300 watt solar cell plugged into a 300 watt inverter vs (2) 300 watt cells plugged into a 600 watt inverter? I would be curious to see how the inverters scale up. Perhaps the home inverters are put out cheaply to encourage people to buy them, but they could be inefficient. Would it simply be cheaper to have a lot of cells tied into a single inverter?
If you check into those numbers, it might give a better idea of what is better.
Now you have me thinking… like you always do… I’ll have to look more into this.
John,
I see 3 factors – and I will have to get back to my Uni E.Engineering days to get the maths for you
a) the cost of Growth – that is how much it costs to add additional capacity to the existing systems – if our energy usage is growing we would need to ensure that this is covered in one form or other – is local the MOST cost effective way of adding this capacity ? Related to this would be the lifecycle costs of the existing systems.
b) the efficiency of the transmission system – pushing energy over long distance is the reason that is given for the localization of generation capacity – however that effect start’s being true over modest distances (I’ll have to look this one up) &
c) the relative efficiency of individual vs larger scale wind or solar.
Let me get back to you on some of these – you know where to find me.
What I can see is that there will be different answers based on how fast the energy demand is expect to increase (or if there is increasing demand at all), however I’m with you – larger scale, more efficient systems would seem to make more sense, however I would want to see how growth plays a part in the “equation”.
Matthew
Hey John,
I think you’re right to trust your inner geek on this. The need for alternative energy has become so demanding of late that unfortunately, the whole concept has become somewhat of a buzzword. I can’t help but be reminded of the auto industry in the 90s claiming to be investing in alternative energy to reduce the backlash from the fossil fuel epidemic, while in reality they were investing solely in fusion (with the understanding that it was still decades from being feasible).
While I love the spirit of the campaign for renewable energy, I just can’t help but feel like the science isn’t there yet. The big number for me is 30% — the maximum theoretical efficiency of a solar panel due to quantum limitations. Silicon’s bandgap really isn’t setup amazingly well for the solar spectrum so most of the energy absorbed is lost to phonons. As it stands, 30% is just a theoretical limit — commercial panels haven’t even gotten there yet. The few research endeavors that have made it close are not any where near economically feasible. There are always other considerations that get swept under the rug as well. For example, how do you clean a solar panel? (http://www.bu.edu/ece/2010/09/03/mazumder-on-bbc-news/)
Some math (stats from Wikipedia):
World energy consumption: 474E18 J = 1.32E17 W*H
Max terrestrial solar irradiance: 1.413 kW/m^2 (let’s assume 18 hours direct sunlight… 25.34 kW*H/m^2)
Solar panel efficiency: < 30% (max possible, not necessarily possible or economically viable)
Necessary solar farm size: 1.58E13 m^2 = 1.58E7 km^2 = 1.67 times the size of the Sahara desert….
My colleague tells me that he had heard stats (considering solar insolation into the calculations) that decrease the necessary farm size to a tenth of the Sahara, but even still, that's a lot of area. Furthermore, some really nasty stuff goes into those panels as you alluded to earlier. There is certainly no domestic opportunities for a massive solar farm of this size, which means we would have to play nice with other countries…
At this point I look at discussions of regulation of a potential alternative energy grid a little bit like creating traffic control regulations for personal aircraft… We're just not there yet. If people go off the grid, they may be able to support themselves, but how do you power public institutions with massive loads? I think the research needs to catch up, and in the mean time, we need to concern ourselves with increasing efficiency… Exajoule is a scary word.
Hope this helps. I won't dare to touch wind power — Mech E was never a strong suit for me. I loved your post about Tesla by the way. Give every one my best,
Jeff
Elon Musk is trying to do the same with his company: SolarCity. His business model is to do the installation free for the customer and recoup his investment during the power generation phase. It sounds like he has trod the path you are researching. See: http://www.solarcity.com/residential/solar-ppa.aspx
There are a lot of “empty” roofs out there that could be put to use.
John
My thoughts…local solar tends to be most efficient on those hot/sunny days that tend to drive up electricity usage, so we may see some peak load smoothing, especially as more people add more airconditioning over time. Small scale local solar (and probably wind, as well) and the subsidies being provided are serving as a forcing function to help drive enough demand to push dollars into research and innovation. So, will small scale solar “fix” our energy problems in its existing form? No. But, I won’t rule out it contributing to future breakthroughs in efficiency and reduced toxicity panels going forward.