ledow said:
It just annoys me as a mathematician... you don't need to be a genius to do the mathematics but nobody bothers. It also annoys me as an amateur scientist - solar and wind are *STILL* a humungous waste of time on anything other than stupidly large scales where they *JUST* make energy "profit" for an enormous amount of effort.
Yes, the *highly* efficient, top-of-the-range solar panels in good-sunshine spots can do lots of great things - power satellites (virtually 100%, but without any atmosphere in the way), power towns (with huge fields full of them and the associated maintenance costs) or power your house (if you can afford the £100,000 up-front cost and are prepared to take the chance that you'll not need to do many repairs over their operational lifetime).
However, 99% of suggested uses and places that sell such things don't realise that all they are doing is making the situation worse by producing some *horrible* chemicals, slapping them into a solar cell, selling them to joe-public, who thinks they are saving money when in fact over their operational life, they could have bought the equivalent in AA batteries or pulled off the grid and not incurred anywhere near 50% of the cost, unreliablity or production emissions (not to mention landfill).
The best example I've ever seen was in my local B&Q (DIY hardware store). A "fit-it-yourself-to-save-money" 2KW wind turbine that was bigger than my car. Aside from planning permission, fitting, connecting to your electrical setup, batteries, ongoing repair costs (ten-foot-wide blades don't take kindly to high winds or just general wear and tear), etc. the damn thing would never (not even at "theoretical maximum", assuming fixed/rising grid energy prices, etc.) recoup the initial outlay of just the device itself within its theoretical operational lifetime (five years, I think it said) if it operated 24 hours a day.
Solar - great for your calculator, but make sure you have a battery in it as well. My calculator has had a solar panel in it since the early 80's, we haven't progressed much since then. Give it another 5-10 years and either it'll work as advertised or it'll be replaced by something that does.
Solar power is great if it is used properly. Photovoltaics (PV) aren't very practical in most situations. Solar heat and solar electricity generated by solar heat is very good. As I pointed out earlier, PV is good in southern latitudes, especially CA due to their tiered rate structure. In this scenario, the cost of electricity goes up as use increases. So you could buy a small system that takes you out of the 2 top tiers and save a lot of money, especially with tax incentives. The energy recoup times is usually only a couple of years and the cost recoup time is about 7 years (at the top tier rates).
Solar hot water is feasible in most of the US as is solar heat, especially when designing a new house. You can implement passive and active solar heat + add solar hot water. In the lower latitudes people could get boiling water from their solar hot water. Mixing solar heat and solar hot water with geothermal and passive solar in new home construction will save quite a bit of energy and will quickly pay for itself.
Installing commercial generation stations in the south, especially the desert American southwest is a great idea and is being done. They are just the beginning and as low heat electric generation matures you will see it become more and more efficient.
There are also projects being done to use fiber optics to light buildings during the day with solar. Solar concentrators reflect sunlight (minus the IR band) onto collectors which route the sunlight into office building and department stores. The natural light looks better and works with peoples bio-rhythms much better. The light is soft in the morning and quitting time and harsher during the rest of the day. Workers are shown to be more productive and store displays look better under this natural light than artificial. It also works on a blend, so on cloudy days the building isn't effected (it just uses more artificial light).
Wind has major problems due to the intermittent nature of wind and with the fact that the winter is more windy than the summer which is when electricity use goes way up from air conditioning. I have heard that every megawatt of wind energy put on line has to be met with a megawatt of conventional generation. There is a project being designed right now that will put a wind farm off the coast of Maine that has 100% wind during the winter and since there is so much electric heat up there, all of New England's heating can be met with this farm. It's supposedly the windiest spot on earth during the winter. We will see what happens.
My big hopes are on Algae and other bio-mass and that PV will improve as more and more people buy it and give the companies R&D money. Hydrogen is a dead end. and their needs to be replacement liquid fuels. Even if we got radiation free fusion and could generate more than we need, hydrogen (which is made from electrolysis) is still too dangerous. Electric cars have too many problems and are unlikely to be resolved in the foreseeable future. Imagine the nightmare of batteries. There is no existing battery technology that is ready for electric cars and a replacement liquid fuel is needed. Switchgrass and Algae (especially Algae) are very good for replacement liquid fuels. Algae can produce Airplane fuel (Kerosene), Diesel and Gasoline and can be "farmed" anywhere, not just on our valuable farm land. It can also be done with salt water. Imagine an algae farm in the desert using salt water irrigated in from the ocean. It also grows very fast and doesn't have a once a year crop. More like every couple of days which is constant supply.
Besides renewables, there isn't any new energy sources on the horizon (except maybe fusion) and we are going to have to diversify since no one solution can replace ff. If we want to keep our modern society, replacements to FF needs to be found and since we don't know any other magic bullet that oil was/is, renewables and lots of them will have to be made to work.
Polossatik said:
Charging a battery seams to have about 75% efficiency (or worse) when charging, aka to fully charge an 7.5 watt battery you need at least 10watt "input".
So if you first charge a battery to use that later to charge a other device then you lose already at least 75% in the "inbetween" battery, then pumping energy into something like a pandora looses another 25% at least... not counting losses in voltage convertors etc
Charging a battery is very efficient (approaching 100%) when the battery is near dead and remains so until about 70% charged and then the efficiency drops like a stone, giving an AVERAGE 75% or so efficiency (ni-ad and NIMH. I'm not sure about Li-ion). IF you charge your batteries to only 70% or so, the efficiency is great. There is a book on the internet called batteries for dummies or something like that and it's great for understanding batteries, maintenance etc. You may want to check it out.
Chris