36 votes
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Why don't they make playgrounds generate electricity?

Because a playground equipped with generators would probably not be much fun. The merry-go-round would grind to a stop the moment it is no longer being pushed. The swings would not swing; they would ...
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  • 2,739
14 votes

Why don't they make playgrounds generate electricity?

A better target would be gym exercise machines Indoors, not exposed to elements, controlled environment so less chance of theft and vandalism. Customers stay on machines for a prolonged period ...
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  • 141
11 votes
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Transmit solar over multiple time-zones?

Yes, we can. Estimates vary of the losses in long-distance HVDC (high-voltage direct current) transmission, but they're around 3-4% per 1000 km. Now, those operate at far higher voltages than you've ...
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11 votes

Why don't they make playgrounds generate electricity?

Playground equipment is very expensive and not typically something that local councils have large budgets for. Hooking it up to the electrical grid for minor amounts of electricity generation would ...
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10 votes

Should we leave all fossil fuels in the ground and not use them?

Yes, we should leave the larger part of all known fossil fuel reserves in the ground. Scientists have calculated that if we want to keep global temperature rise under 2 degrees C (which was agreed ...
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  • 14k
10 votes
Accepted

Is electricity used at night more likely to be renewable?

In Ireland, electricity is equally likely to be from renewable sources during the day as during the night ENTSO-E, the European Network of Transmission System Operators for Electricity, provides a ...
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9 votes

How worthwhile is it to use energy during daylight to take advantage of grid-based solar power?

In the purist sense of "the electricity I use was actually generated by a wind farm", your idea is broadly correct. However, unless you actually have solar panels or a wind turbine on your house, that'...
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  • 3,755
8 votes

How worthwhile is it to use energy during daylight to take advantage of grid-based solar power?

You're being quite specific with regard to solar... but in principle, it is possible to move your electricity consumption to minimise its carbon footprint. Ecotricity (a UK "green" energy supplier) ...
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  • 3,601
8 votes

Hydro-electric generation from roof-collected rainwater

If it's a very simple motor then it may be possible just to run it backwards to generate electricity. If it's got electronic controls, probably not. But is it worth it? Do a quick calculation of the ...
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7 votes

Why the world is using non renewable resources?

There is no one reason for why humans are using non-renewable resources like fossil fuels and nuclear fuels to generate energy. I'll write what I know about and others can do the same and from all the ...
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  • 3,152
7 votes

Is pellet fuel a sustainable energy source in the way it's used now?

It depends. It is possible to farm wood sustainably, or unsustainably. Both ways happen now. It is possible to use wood pellets for energy while trapping particulate matter and other non-GHG ...
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  • 14.6k
7 votes

What is the number 1 country by global installed wind capacity: the United States or China?

According to the REN21 Renewables Global Status Report 2014, China had 91.4 GW of installed wind capacity by the end of 2013, more than any other country in the world, of which 75.5 GW was in ...
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7 votes

What is the difference between "hydro" and "tidal/wave"? And what is the difference between "solar (heat)" and "solar panels"?

Beware that chart - it is from 2004, and hence is very out of date! In particular, photovoltaics ("solar panels") have become cheaper much faster than anybody expected a decade ago, and wave and tidal ...
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  • 3,601
6 votes

Can The UK Be Powered Practically By 100% Renewables?

Summary: yes, the UK can be powered practically by 100% renewables Technically it's fairly straightforward. Subject to some fairly reasonable assumptions, and the commercialisation of technology that'...
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6 votes

Are trees more productive than wind turbines?

Wind turbines do not turn the ground between them into desert. There is still farming and growth of various plants (even trees) possible. It should not be excluded in those comparisons and ...
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6 votes

Is oil actually a renewable and sustainable resource, but we just use much too much of it?

What does renewable mean? Wikipedia defines a renewable resource as (emphasis added): a natural resource which will replenish to replace the portion depleted by usage and consumption, either through ...
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5 votes

What's the average efficiency of pumped hydroelectric energy storage facilities?

In this question about rooftop hydro I covered the efficiency question almost as an aside. I can't find an actual plant with efficiency over 80%, only claims that that might be possible. The average ...
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  • 3,755
5 votes
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Is "renewable" a proper term for both solar and hydro power?

There are lots of ways to subcategorise renewables, for example: Indirect + direct solar (wind, wave, hydro, biomass, biogas, PV, CSP, solar thermal, - and what's used up here in all cases is ...
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5 votes

Is solar energy the best renewable source of energy?

The validity of your assumptions depend very much on your location and on the amount of energy you want to generate. Some small-scale solutions do not suffer from the same drawback as large-scale ...
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5 votes
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Cost benefit analysis of a PV array with racking to set optimal angle, vs a larger array

According to the New Zealand Ministry of Business, Innovation, and Employment (pdf), the average home in New Zealand uses 7,046 kWh per year, and pays a rate of $0.2879/kWh (NZD). I used this as a ...
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5 votes

Are trees more productive than wind turbines?

A tree farm of that size in a temperate climate would only produce ~1.7GWh/y (net). You are overestimating the productive value of trees by a factor of ~15. A 5MW wind turbine can produce a maximum ...
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5 votes

Why do some people say that biofuels are renewable energy source if producing biofuels requires nitrogen fertilizers?

They're called renewable because it's possible to do them in a renewable manner. Specifically, the energy in them comes from the sun, in a fairly short time span (i.e. years, rather than millennia or ...
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5 votes

How much land needed to dispose of blades from wind turbines?

This wont answer your question, but will attempt to show, why the question is based on wrong assumptions. That headline you're concerned about is missing a "yet". True, currently recycling ...
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  • 547
5 votes

grid-based gravity assist power generaiton

I think you have exactly the right term already. The Institute of Electrical Engineers use "gravity energy storage" and wikipedia has a Gravity Battery page. The main issue is that pumping ...
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  • 3,755
5 votes

Why don't they make playgrounds generate electricity?

There are two main areas to consider here: Safety. Anything put near children has to be safe, and mains voltage and generators generally aren't. Damaged wires could electrocute somebody, a generator ...
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  • 51
5 votes
Accepted

Do solar panels generate more electricity in hot or cold climate?

If the amount of radiation stays the same, solar panels produce more energy when they are cooler. Heat causes efficiency to suffer. However, this is assuming the radiation amount is the same. Usually ...
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  • 2,874
4 votes
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What's the applicability of biochar?

No, and no. Current production costs of biochar are in the hundreds of dollars per tonne. (It shouldn't be that expensive.) By comparison the mining costs for coal at my neighbor, the coal mine, ...
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4 votes

What is the difference between "hydro" and "tidal/wave"? And what is the difference between "solar (heat)" and "solar panels"?

Hydro power uses dams (or at least a pipe where one end is as much higher as possible than the other) to use the pressure of water at the bottom to turn a turbine and generate electricity (or ...
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4 votes

Does a PV panel take more energy to build than it generates in its lifetime?

Yes, PV is viable. That's why somewhere around a billion solar panels have been connected to the grid - about 200 GW of capacity, with another 50 GW or so coming online in 2016. I'm afraid that the ...
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