OK... I have checked up some figures with my sister-in-law, who is interested in such things.
First generic comment. There is no silver bullet. If anyone, for any reason, is particularly interested in reducing their impact on the planet, the most effective single thing you can do as an individual is anything that reduces your own consumption. The things we are speaking of, like painting a roof white or installing solar power, are other minor changes you can make as well.
Be that as it may, what turns
me on in particular is not saving the world, but learning about it. That's just how I am wired, maybe.
So... assuming we are fascinated by the physics and the numbers, here we go.
Here in Newcastle, a domestic solar power system is commonly about a 1 kWatt system, which covers 6 square meters and actually gives you roughly 4.5 kWhours/day, averaged over all year. Continuous power there means about 190 W. That's if you've done it well.
The power you generate feeds into the grid, and what you don't use yourself at the time gets knocked off your bill. Economically, it does have a substantial impact on your power bills.
However, it's not "efficient" when measured against the sunlight hitting those panels. You get roughly 180 W/m
2 at the surface, and so with your 6 panels you are squeezing the juice out of about 1080 Watts. So you are getting about 17%. I'm actually surprised it is that high; but so be it.
A kiloWattHour (3.6 MJ) of power generates order of magnitude 1 kilogram of carbon dioxide in emissions; and so running your solar system for a year generates about 365 * 4.5 or about 1640 KWhr, and so saves about that many kilograms of CO2.
From the calculations I gave in [post=2295904]msg #38[/post], one kilogram of carbon dioxide can be taken as altering the energy balance of the Earth itself, so that an extra 0.9 W is absorbed; but remember not all emissions STAY in the air, and so you should probably reduce that impact by about half. Let's say the 1600 kilograms is worth about 800W heating on the Earth's energy budget. It will vary depending on your local power generation; it varies quite a bit between different states in Australia. But 800W less greenhouse heating for your year's worth of solar panel sounds in the ball park.
As a result of running your panels for a year, you've avoiding adding another 800W to the Earth's energy balance, just from the reduced CO2 emission.
Now you could also have painted your 6 square meters white. Had you done this, and increased albedo by 0.5 or so, you could have saved reflected some 6*180*0.5 = 540 W or so.
The thing is, your panels keep working. Not forever, but you'd better hope to get several years out of them! Bottom line -- for Earth's energy balance, a solar panel is better than a white roof of the same size.
Or you can just save power. Households vary a lot, by 8000 kWhrs in a year is credible. If you cut this by 20%, you have 1600 kWhours in a year; which is your 6 square meter solar system right there.
Or you can drive less. Cars can be from about 0.1 to 0.4 kg CO2 per kilometer, and I'm figuring about 0.45 W in the energy budget per kilogram. So 10,000 km in your car is from 1000 to 4000 kilograms CO2, or 450 to 1800 Watts added to the energy balance of the Earth. Or just get the more efficient car.
Here's the summary to help it stand out. The following seem to be about the same value in terms of their impact on Earth's energy budget, of roughly 5400 Watts in the energy balance to the Earth.
- Having 60 square meters of white roof. (But you have to KEEP it white to keep up the 5400 albedo effect.)
- Having a 6 square meter photovoltaic system in operation, working for 6 years. Even if it breaks down after that.
- Cut your energy bill at home. Cut an 8000 kWhr/year bill by 20%, for 6 years.
- Drive less. 30,000 kilometers less in your gas guzzling SUV, or 100,000 kilometers less in your subcompact.
- If you drive 10,000 kilometers a year, replace that SUV with the subcompact; and in 4 years or so you've got that impact.
Checks on my figures actively solicited.
I have not factored into this the energy consumption in actually MAKING and installing panels. Which is significant. Solar panels do help... but they are a big expensive complex system to set up, and straight impact-wise, one of your least efficient strategies. But that's okay; there's no silver bullet and you can do all kinds of things if you really want. The solar panels do help; if that's your interest.
My sister-in-law HAS installed solar panels. 9 square meters of photovoltaics, and another 6 square meters on the Granny-flat for my Mum and Dad who live on the same block. Plus she's recently built an extension (as an owner builder) and in the process managed a lot of passive heating and cooling, with the best ways to manage insulation, grey water reuse, air flow, etc, etc. And they are trying to slash energy use. They want to get to zero on their energy bill, and that seems possible. And now she's doing a course to help do formal assessments for others. She's paid by a public government supported program, and anyone can get the assessment for themselves, which is mainly about saving your own bills. In the future, a basic energy assessment will be a required part of the information when you sell a home, much like a building report. And Cathy will be able to those as well.
So there you go, folks. If you are interested, there's lots you can do. But look first at your insulation, and where you can switch off appliances (don't leave the computer or the TV on stand by; switch it off if you aren't using it and save yourself some money), and consider public transport where feasible. Look for a holiday destination in your state rather than overseas. Solar panels if you are keen; but they don't matter as much, or save you as much money, as just seeing how you can reduce your energy bill by using less of it.
Cheers -- sylas
I don't understand the question -- too vague.
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