I have installed on my roof a 4200 W solar system. It's been in operation for about three years now. It's installed cost (grid tie - no batteries) was ~$30K.
On a really good day the system produces ~24KWhrs. My home uses on average about 24 KWhrs a day. Significantly more if one turns on the AC (sometimes required during the summer). Average daily production over a year runs around 13 KWhrs.
Snow on the panels cuts output dramaticly. I go out with a roof rake to try and clean them off. About a 1/2" of snow cuts output to nearly zero (39 Watts typical).
Cold weather makes the panels more efficient, but the big seasonal effect is just plain fewer hours of daylight. (I live in New England).
The panels I use are rated at 14.6% efficiency under "Standard Conditions". For a signifincantly higher cost you can get commercially available panels with claimed efficinecy of 21% (SunPower). The solar cells claiming efficinecies of 30-40% are concentrated cells (ie needing a optical concentrator lens). These cells only work in very high brightness sun conditions since there efficiency requires a high operating temperature. There manufacturers recommend them for high sun areas like the Southwest. Obviously they are very expensive, since they require optical lens assemblies.
For reference, "Standard Conditions" refers to 1000W/square meter illumination with surface perpendicular to solar input. I don't remember the temperature off hand but it's something like 25 degrees C.
I just thought I would present some hard data to this dicussion.
Thanks for your real-world perspective, LetoAtreidesll. It's always good to hear fromour reader experts who have this type of experience to provide context for some of the new technologies being introduced and researched.
From building and operating a small 2KW system (built 3 yrs ago) I can tell you from experience the tech still is not viable from a economic standpoint.
Sure you can build them and they work but the costs vs return are outrageous. I am not just talking the installation and purchase price but their are many cost often left out of the reports such as large maintence and upkeep cost these system do not maintain themselves and require preventive maintance as well as repairs and unlike a large generator or even a big turbine their power output is small so were a gas turbine could power 10,000 homes and a small force of 20 total employees maintain 5-7 of these (their is just this kind of plant 40 miles to the south of me with 18 employees and 5 generators) to supply that many homes you would need hundreds of acres of land and a very large workforce to maintain clean(yes for opt eff cells need cleaned they are glass by the way), PM'ed, protected yes a large solar field requires security guards to protect their assets, repair.....etc. These cost only increase as time goes on. And unlike the turbine that works day and night through rain and snow the solar field only produces solid power from a few hours after dawn to a couple hours before dusk on days were the sun shining solidly on cloudy rainy snowy days you end up with 20-40% power.
Solar is a great tool but is by no means the solution at least not for a long time it needs so many additional puzzles peices before it will truely be viable from an ecomonics standard. This is not to say the heavy hand of Goverment can not force it but that only hurts all the people as it can only result in large cost increases for power.
""Spectrolab, a Boeing company, is making and selling 38% and 44% concentrator cells to the space market."" Really you are going to try to make a conspiracy because the space bases cells are more efficeint. Well if i must explain common sense then lets do it. With a space cell it is optimized for a very different enviroment then an earth based cell plus cell cost is not important light and high power is they do not think twice of have a 10% gain in power that costs 2000% more. Space cells do not need to worry about over heating, hail, wind, snow load, bird droppings, oxidation, corrision, need I go on.
I did not know about this company Spectrolab, Trenth. That is really interesting to me. I will have to look into it. If this sort of technology can trickle down to the more mainstream markets as well that would be a real breakthrough.
I think 2014 will be a breakthrough year for solar technology. All of the evidence points to not only improved efficiency out of existing solar-cell technology but also new materials and ways of designing cells that will further improve how they work.
Spectrolab, a Boeing company, is making and selling 38% and 44% concentrator cells to the space market. They have very high reliability. I think it's just markets. They don't want to compete with cheap panels till they have to. They are expanding and decreasing manufacturing costs. But why would they want to fight the US gov promotion of fossils and nukes, the utility attacks on solar, and the cheap Chinese panels? They own the military space market.
If our gov would stop propping up the fossils and nuclear industries and start really energizing the solar, wind and waste to fuels industries we would make the transition to renewables much faster.
Besides there is no shortage of rooftops and parking lots for existing solar to supply more electricity than we currently know what to do with. More efficiency is a red herring, it's a marginal benefit.
Germany is paying it forward. They are putting their money into solar, wind and waste to heat electricity and fuels. Instead the USA is still plowing money into fossils and nuclear and keeping the prices artificially low and delaying the switch to ultimately cheaper renewable power.
Here's a rebuttal of the De Spegal and NY times articles. http://cleantechnica.com/2013/09/20/new-york-times-gets-big-red-f-germanys-renewable-energy-transition/
Did you think the fossils and nuclear industries would go quietly?
They don't like losing out to solar and wind, is that a surprise? They the core of their argument: it's really rough on their industry.
Gas turbines ramp up and down just fine, that's why they are used for peaking and backup, but the companies that own them, don't make as much money if they are not used all the time. Same for Hydro.
Hydro kills fish, and there is very little available new hydro in the USA. Maybe the underwater turbines will pan out, but not yet.
Hi Charles, these figures are bandied about globally by some governments and pretty much all providers, so either they have merrit or someone dreamt up the figure and everyone is jumping on that bandwagon that it suits. I only make this last statement for readers to remember that there are a lot of people that don't do their research properly either for convenience or laziness.
Anyhow over to other aspects of this, I've seen figures quoted higher than 30% for PV panels for maybe 10 years or more but the panels actually being sold never seem to be better than a tad over 20%, maybe 25%. This means either that the cost of getting these 40%+ efficiencies is so high it doesn't pay for the difference OR the innovation kills the reliability OR the conditions needed to get this efficiency are unrealistic in a real world like say < 1 degree offset from the perpendicular OR there's just a hell of a lot of work still to go. I think a detailed analysis of past failures to get to market could be very interesting.
Getting back to PV's, or any renewable energy the big clincher is always going to be storage, more storage and maybe more storage. With PV's the efficiency might be 44.7% but I'm sure that's for perpendicular light and so either a lot of panels at different angles or a direction adjusting system is going to be needed. Also based on my experience with our PV installation you need enough over capacity to get your required power on a heavily overcast day. We exceed our winter electricity usage from about 10:30 and drop below that level again after about 15:00 and in summer probably from 7:00 to 17:00 and inbetween that we produce 3x more than we need contributing to business peak use but not to residential peak use so I have to wonder how efficiently our spare kilowatts make it over to the business districts?? But if it's overcast we only get about 500W to 1kW out of what is a 4kW rated system, so 1/8th to a 1/4 during the peak light periods. This really does make the 15%-30% projections you mentioned sound realistic not including the zero input from PV's overnight.
Don't get my ramblings wrong, I still believe we need to go renewable, just that we need to do a lot of thinking about how it's going to work.
Finally, thanks Elizabeth for an interesting post, it's good see the world is plodding on despite a few setbacks.
Linear guides are one of the most important components required for the development of automated or computer-controlled equipment. Aluminum profile extrusions, used for these guides in machine design, can enable designed-in functional features.
Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.