Pierre: I thought of a different answer to one of the questions questions. If you know the average insolation where you live you can assume my 1/6th as the best performance with brand new panels. As an example, 180 W/m2 / 6 = 30 W/m2. It gets worse afterwards, slowly if you clean the panels frequently, rapidly if you do not. At 1/2 life, efficiency may drop below 10 %. Stan
On Fri, Sep 9, 2011 at 8:50 PM, Pierre Abbat <[email protected]> wrote: > On Friday 09 September 2011 11:33:08 Stanislav Jakuba wrote: > > Note: This e-mail was apparently "blocked" as some of the earlier ones > > were. Here is a new attempt. > > In "into", the first three letters are bold and the last isn't. > > > but the units are kWh/h, Btu/hr, hp, V·A, and others but rarely the W > > kW·h/h is of course kW. You may have meant kW·h/d. V·A is dimensionally > equal > to W, but when motors are rated in volt-amps, that's not equal to watts > because the volts and amps are out of phase. The wire still has to have > capacity to carry all the amperes, even those that don't contribute to > power. > > I'm designing a solar house. I took a spring power bill to get a rough > estimate of my electric consumption. The bill said I used 391 kW·h in a > month, but I'm not sure how long that month was, so I had two estimates > (526 > and 543) of power consumption in watts. But a 550 W panel is not enough. I > have to know how many hours per day the panel is producing electricity - a > rule of thumb says 5, but it varies with season and location. Solar > designers > often use a figure in kW·h/d in this calculation. > > In your solar calculation, the 200 W/m² figure includes the 5 h/d. > Insolation > at noon on a cloudless day, with the sun's rays normal to the panel, is > about > 1 kW/m². For the hour per day figure, you should take not the yearly > average, > but the least monthly average, which is probably the one in December in the > temperate north. > > What do you do in your house that takes 4.6 kW? I had two computers running > continuously (three now, the third being a laptop, and soon a fourth which > will be for my work), a water heater (my house will have it built into the > roof), and a fridge (I'll get a more efficient one designed for a solar > house). > > I've seen a solar panel comparison which lists watts per square foot. That > irks me. Insolation is quoted in watts per square meter, and my lower slope > is 20.6 m (plus end eaves) by 3658 mm (i.e. 12 ft, a common lumber length). > > Another unit you may want to mention, though it's neither energy nor power, > is > the ampere-hour. Battery capacity is quoted in this, instead of > kilocoulombs. > And to build a battery box, I'll have to find the dimensions of the > batteries > in millimeters. > > If you'd like to discuss solar design, feel free to contact me off-list. > > Pierre > -- > gau do li'i co'e kei do > >
