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11

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 mentioned: you wrote of 10 000 V, which is also written as 10 kV. HVDC runs at 100-800 kV, i.e. 10 to 80 times higher (100 000 to 800 000 V). The idea of using ...


11

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 upon in the Paris climate agreement), then we cannot use more than 1/3 of all currently known reserves. ...globally, a third of oil reserves, half of gas ...


9

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's not how the system actually works. Broadly, all the electricity generators feed into the national grid (which in Australia covers only Qld-NSW-Vic-SA, but ...


9

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 transparency platform where you can see the hourly actual generation per production type for Ireland: It's hard to pick out a trend just by looking at a day ...


8

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) have a web page that shows the current carbon intensity of UK generation1, and gives a red/amber/green indication of whether you should turn stuff on now. If you ...


7

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 pollutants. This sometimes happens, and sometimes it doesn't. It is possible to dispose of the resulting post-combustion products in a way that returns the nutrients ...


7

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 amount of energy available. How much water are you expecting to fall? (roof area x annual rainfall). One cubic metre of water weights 1000 kg. Height (metres) ...


7

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 answers you'll be able to see complexity of the situation. To begin with humankind has been burning things for energy for millennia. It's something we know a ...


7

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 power have proved more difficult and costly than some had projected. Here's some more up to date info on costs: http://www.eia.gov/forecasts/aeo/...


6

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 commercial operation. The USA had 61.6 GW of installed wind capacity. In terms of actual generation from wind, the USA was world leader in 2013, with 19.4 GW mean ...


6

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 efficiency will be much lower than the peak, as a lot of plants are old and have efficiencies around 60% (although some have been refitted to boost efficiency). ...


6

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 incoming solar energy), versus others (tidal & geothermal) Combustion (biomass, biogas) versus others Heat engines (geothermal, biomass, biogas) versus others ...


6

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 solutions. Biomass The CO2 emitted by burning biomass is CO2 from the atmosphere that was taken up by plants and trees. This means that energy from biomass can be ...


6

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 starting point to set up a simulated solar array using PVWatts, a very useful tool developed by the U.S. National Renewable Energy Lab. I set up a system for ...


6

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 calculations. A wind turbine with 3MW power, rotor diameter of 100 meters rotating at a hub hight of 100 meters may allow growing plants with a height up to 25 meters (~ ...


5

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's already proven in the labs, it's also economically efficient too. Total UK energy demand is about 200 GW, of which 40 GW is presently served by electricity. ...


5

Generally, the situation is becoming less sustainable. The demand for large scale electricity production with wood pellets is rising faster than their production, and ('fresh') trees are being used in their entirety for the production of pellets. Calculate the energy required for that production + worldwide transport and any ecological advantage quickly ...


5

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 of ~44GWh a year. Your assumed figure of 1GWh is only 2.3% of its rated capacity. No-one would bother financing/building a turbine on that site if they could ...


4

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, run about 90 cents (canadian) per ton. It will be a while. General paper about biochar with nominal $200/ton wholesale price from a unit that processes 2000 ...


4

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 occasionally, do some other work such turn a mill). They are often located on the edge of a large lake in a mountainous area so that even when there hasn't been much ...


4

Measuring impact I've yet to see a meaningful metric that relates directly to materials, other than the EROEI (Energy Returned On Energy Invested); and there's discussion about whether or not EROEI is at all a useful measure: its probably not that useful, since once it's over 1.0, it's completely subsumed into the economics. The same would be true of a more ...


4

You must open circuit the panels you're not using, do not short circuit them. Open circuit is fine, the panel just sits there and no current flows. You'll see quite a high voltage on the terminals (it'll be listed on the panel data sheet as "maximum open circuit voltage". If you short the panels you'll get up to "maximum short circuit current" which risks ...


4

To add to @Fred 's answer, there are a few things that can easily be overlooked. In order to generate clean green energy you need to invest into these power production facilities. Obviously we know these are expensive, usually more expensive than fossil power plants. So for the price-per-power green energy isn't that interesting. Sun provide low amounts ...


4

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 costs you have are quite wrong. Remember, PV generates electricity - that's a higher-quality (high exergy) energy than heat from gas. To get electricity from ...


4

From the Wind Measurement International site: P90 is all about quantifying the uncertainty of annual energy yield predictions. P90 is the energy WMI predicts that a wind turbine is 90% likely to produce over an average year, given the uncertainties in the measurement, analysis and wind turbine operation. P50, on the other hand, is the average annual ...


4

I have some knowledge in this field, coming from several years' experience in drafting and defending patent applications that deal with wind turbines in one form or other. If you're talking about a single wind turbine with a sensor somewhere on the nacelle, downwind of the rotor blades: one way of dealing with the problem of wake-corrupted measurements is ...


4

There are very few grids with high penetration of those exogenously-variable renewables that have up til now provided no inertia to the grid - wind and PV. What matters is not the penetration in a particular market, nor in a particular country, but rather what the penetration is on a particular synchronous grid - the area over which the frequency is ...


4

However, in the cases of wind, solar, and geothermal, this isn't so obvious -- nothing is being used up (at least not in a measurable quantity) which would need to be renewed. Furthermore, there's no need to manage wind, solar, and geothermal energy -- it isn't possible, on human scales, to overuse these. For wind and solar there isn't a "store" ...


4

Renewables shouldn't be thought of as an either / or proposition. If we're thinking about an entire economy you want a variety of sources at a variety of scales, with a variety of storage systems. The availability of individual solar panels, wind turbines etc. can vary a lot over time. But with a sufficiently distributed network the availability becomes ...


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