# Tag Info

31

The exhaust gasses are compressible fluids, whereas liquid water is not. Here's an animation of how a gas turbine works: https://www.youtube.com/watch?v=gqNtoy2x5bU At the combustion stage, the gas and compressed air are mixed together, already at high pressure. The burning releases the energy stored in the gas, heating up the released gasses (exhaust). ...

30

Because most of the water is at the lowest point is can be, the ocean. Second issue is that you need quite a bit of vertical drop for water power to be a viable power source. There are DIY hydro power setups but they include diverting part of a stream through a pipe into a turbine down the hill, but those tend to only be enough to power a single household ...

15

Not everything scales linearly. In particular, the cross-sectional area of supports required scales faster than height of a structure, all else held constant. This explains why ants have tiny thin legs compared to elephants. An ant linearly scaled up to elephant size would not be able to stand, or would snap its legs trying. The same thing happens to ...

15

There are no silver bullets when it comes to decarbonising the grid. That's good news: it means you can stop looking for one, and accept that every form of generation has its pros and cons. Concentrated solar power [CSP] relies on direct sunlight. Not just ambient daylight, but lots and lots of direct sunlight all year round. Whereas ordinary photovoltaics [...

11

There are two issues, harnessing and market. You need both to be viable. A market, makes most of the 70% of the land mass covered by water unusable, because even if you could harness the power, it is impossible to get the power to consumers. There are no practical storage alternatives, either. Ocean buoys do harness ocean currents to meet their ...

10

Everything we do as humans has consequences of some sort. Although not a huge downside (in my opinion), critics have often cited the plant's supposed adverse effects on wildlife: Wikipedia Article: It has been noted that insects can be attracted to the bright light caused by concentrated solar technology, and as a result birds that hunt them can be ...

9

In the UK, the sun does not shine every day. We also need the most power in winter when the sun shines the least. Therefore every solar power station must be backed up by anther power station that can work when the sun is not shining. Concentrated solar power allows short term storage of the steam, so at least copes with 5 minutes of cloud cover, it ...

9

It's not a simple relationship. First let's deal with the kinetic energy of the wind passing through the rotor. The mass of air passing through it in one second, $m$, is equal to the the density of the air ($\rho$), times the surface area of the rotor (${\pi}r^2$), times the velocity of the air ($v$). i.e. ${\rho}{\pi}r^2v$. The kinetic energy of that air ...

9

As it happens, I just recently went through that calculation myself for a different site. Given the following facts from a quick web search, it isn't difficult to work out the numbers. The maximum efficiency of a (large) windmill is about 40%. The density of air is 1.225 kg/m3 You need about 50 mW (10 mA at 5V) to light up an LED First, we'll need about ...

8

Rivers in a flat landscape are often unsuitable because you need a height difference to make the turbine work. Let's say a 1 meter height difference is required. There are many areas where the river's gradient is so shallow that raising the river's level by 1 meter would inundate everything for miles around, so you'd need to build a dam to contain the river. ...

7

Those aren't "smoke" stacks but cooling towers designed to let hot air rise and expand optimally. These things are typically 200 m high. Static pressure of 200 m of water is pretty high. They were never required to be water tight so they will leak. In fact towers are open at the bottom to let air in and rise inside. So to start you would need to seal that ...

6

What's missing so far is an explanation why you can't expand from high pressure to atmospheric in a single stage gas turbine. There are two types of gas turbines - impulse and reaction turbines. Both face the same problem but it's easier to understand in the impulse turbine. An impulse turbine accelerates the gas through a nozzle from high pressure P1 to a ...

6

So, this battery costs US$70, weighs 406 grams, and holds around 200,000 Joules of energy. To get the same energy from that weight as a "gravity battery" you'd have to pick it up over 49 kilometers into the air. There are applications where picking stuff up and powering things as it falls is useful -- the gravity-powered lighting for 3rd-world countries is ... 5 Something can only be 100% efficient when a lot of generous assumptions are taken into account. If you assume: No friction (turbine surface, turbulence, nozzle, or bearings) Perfect cup design (100% 180degree jet reversal) A dry wheel (no water is spun off) Not counting the gravitational potential to drop the water away from the wheel in the efficiency ... 5 The cost of a wind turbine is not proportional to its size - like everything that needs to be manufactured, the cost exponentially increases as manufacturing becomes more complex, beyond what has been done. In terms of real estate on the ground, building a giant wind turbine may be more efficient (maybe not in fact, because stability issues may require the ... 5 You seem to be asking about using fruit juice as the electrolyte of a battery. Yes, that's possible, but you don't get a lot of power that way. The power also doesn't just come from the fruit juice. That's only one of the chemical reactants. One or both electrodes are the other side of the chemical reactions. The EMF is a function of the battery ... 5 Given that water is roughly 1000× as dense as air, and incompressible besides, it should be fairly obvious: A wind turbine would be destroyed by the forces that water would put on it, and a water turbine wouldn't even notice the forces created by wind. 5 The energy cost of obtaining Deuterium and Lithium is minimal compared to the energy released by the fusion process. There are many references that provide relevant information but a sensible one to refer to is the official ITER site "Fusion for energy". Fusion for Energy (F4E) is the European Union’s Joint Undertaking for ITER and the Development ... 5 The math doesn't make any engineering sense. A 5MW turbine typically rotates at about 10 RPM, near enough 1 radian per second. Assuming you had reasonably big sprockets on the chain drive, say 2 meters diameter (!!) the linear speed of the chain would be 1 meter /second, and the tension in the chain would be about 5MN or about 500 tons force. Something ... 4 You need to push air through the turbine at 11 m/s, or just above. That's what the rated windspeed means: it's the lowest windspeed at which the turbine hits rated power, at standard atmospheric pressure. The volume of air you need is determined by the area of the rotor. Let's say it's$\alpha m^2$. So you know you need to push through$11\alpha m^3/s$. So ... 4 The clutch provides an instant disconnect either for scheduled maintenance or in an emergency. If the water flow is stopped instantly, then the energy of that moving pipeful of water has to be dissipated and can cause a lot of damage. Some systems are fitted with surge pipes for exactly that reason. On one system I worked with, slowing the flow from max to ... 4 Consider 1 kWh = 1000 W * 3600 seconds = 3,600,000 J. 1 kg lifted 1 m = ~10J. Let's use 1 metric tonne. 1000Kg. So we get 10,000 J per meter of elevation. 3,600,000 / 10,000 = 360 meters. Around a thousand feet. Ok. Getting a 15 cm diameter well dug and cased is on the order of \$20/foot. So \$20,000 buys you a 1000 foot deep hole. Use whatever ... 4 In years past I would have been a fan of hydroelectric power but I have read1 about some of the downsides over the years. These include: Major ecological problems including blocking fish migration. Putting in fish ladders or stairs doesn't really work well as the fish can't find them with all the din of the spillways and turbines. Most silt up drastically ... 4 I would like to answer this question slightly differently. The challenge with rechargeable batteries (Lithium Ion), each charge discharge cycle causes internal resistance of the battery to increase. This causes the usable life of the battery to decrease. Therefore if the rise internal resistance over time is decreased or fully resolved then the Lithium Ion ... 4 The U.S. National Renewable Energy Lab did a study of solar installations in the U.S. in 2013 and determined that for large-scale solar PV systems, 7.9 acres (31,970$m^2$) of land are required on average for 1$MW_{ac}\$ of power capacity (from Table ES-1). This is based on analysis of 72% of existing installations in the country, so this is a good real-...

3

Concentrated solar power plants are best located in isolated areas that receive a lot of sunshine all year round, which basically means arid or semi-arid regions. Most of these regions don't have large populations so long power transmission lines will be needed. To increase performance and efficiency, each CSP plant will need to be uniquely designed and ...

3

overview: Renewable energy is one for which the input energy is renewed on human timescales. Remember, energy is always conserved. It doesn't come from nowhere. Pretty much all the energy we use on Earth comes from the stars - and almost all of it comes from one star in particular, the Sun. not renewables: Uranium (for nuclear power) is in the earth after ...

3

The Betz limit will give you a good theoretical maximum from your wind velocity and swept area. Your real world turbine will fall somewhere below this number based on its efficiency. For measuring power production over a period of time, you need wind data for that particular area. Wind data can be iterated and summed for a particular turbine, but generally ...

3

The reason why a hydroelectric generator is fundamentally different to a gas turbine is because water under pressure is not a gas, and does not change size significantly as energy is extracted from it. A gas engine has to account for considerable thermal and volume changes of the gases inside the engine, so multiple parts and multiple materials are ...

3

Water turbines are a major source of electric power. A water turbine generally has only one rotor disk. (from Old Moonraker at Wikipedia) Gas turbines are used in natural gas electric power generators, jet aircraft, and a few other vehicles. A gas turbine generally have lots of rotor disks, which can be divided into two groups: compressor rotor disks and ...

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