## how can solve this question please need help?

(a) One approach to ameliorate the effects of the variability of wind and solar power is the use of energy storage. Calculate the approximate surface area that would be required of a lake of an average depth of 20 m at an elevation of 300 m (mean water level between full and empty reservoir) above an array of Francis turbines, operating at an efficiency of 85%, if we were to store enough energy to meet the
entire power requirements of the National Grid (say 50 GW) for 24 hours
Energy released at turbine, E = force x distance = mass x acceleration due to gravity x distance.
So E = volume x density x acceleration due to gravity x distance.
So E = π.r² x 1000 x 9.81 x 300, assuming that the lake is a cylinder with radius = r.
This gives E = 1.85 x 10^8 x r².
Only 85% of this is converted into electrical energy,
so the electrical energy produced = 0.85 x 1.85 x 10^8 x r² = 1.57 x 10^8 x r². [Joules].

Now 50 GW for 24 hrs. = 50 x 24 GW-hours = 1,200 x 10^9 watt-hours = 1200 x 3600 x 10^9 watt-seconds.
Since one watt = 1 Joule / second, one watt-second = 1 Joule.
So, 1200 x 3600 x 10^9 watt-seconds = 1200 x 3600 x 10^9 Joules.

So, equating the two figures for energy available and energy out, we have:
1.57 x 10^8 x r² = 1200 x 3600 x 10^9.
When we do that arithmetic, we get: r = 5.2 x 10^3 metres = 5.2 km.
► Hence, the area of the lake = π.x (5.2 x 10^3)² sq. m. = 85 x 10^6 sq. metres, approximately.

my question is
b-Comment on the result you obtained in part (a). Your remarks should include your thoughts on the practicability of building and using such a reservoir; what you thought of the assumptions behind the question in (a); and some suggestions for other measures that could be taken to moderate the effects of variability of energy supply

Hey David, kudos on the math work, although I can’t say for certain the calculations are correct, they look good to me. As far as thoughts on practicability, in the years we’ve been learning about and powering our home with renewable energy, one thing I’ve learned is this: The future of power today is a diverse source. People are constantly asking me what’s best, wind, solar, coal? We would be best off if we had a little of each of them. Any disruption in one source, either due to supply constraints, technological changes, or environmental issues, would not be hard to offset. When you rely on oil for 80% of your countries energy source, then a war erupts on the other side of the globe, you have an instant recession, we’ve proven this several times now.

The same can and should be said for energy storage. Many nuclear plants today have a reservoir like you outlined above connected to them. This way, the plant can operate at its design parameters all day and night, and the reservoir can make up for the dips and peaks in demand changes. The storage medium here is gravity, forcing the water up to the top when you have excess energy, and allowing it to fall when you have a shortcoming. But in many cases, thermal could work better. Suppose you build a large thermal solar plant in the desert, that boils water to run a steam turbine. But in the daytime, you have excess power. Instead of venting it off, we could heat oil to say 500 degrees ( it boils at a much higher temp than water, yet stays liquid well below 32 degrees ). Now once the sun goes down, we could simply reroute our water through a water to oil heat exchanger, and continue boiling water with the hot oil until dawn. Now we have access to solar power at night, petty slick. I submit that this type of energy storage would work great in the Southwest United States, Northern Africa, and some other places that both lack water and have excess sun and heat. Consider this in your discussion. This points a large finger at what I like to call, “appropriate placement.” Take a long skinny river with very little flow on a mountain side. Not a great place to make hydro power due to the low output. But as a reservoir to make a gravity battery like the one you outlined, it could be perfect, with a large, high altitude reservoir that powers a large generator intermittently, rather than a small one continuously. It would be a self trickle charging battery that could be recharged by pumping water back in when there was a surplus of energy too. You wouldn’t put one in Phoenix, where it’s flat and dry, but it would be great in Seattle or Hawaii. Lots to think about here, good luck David, Rudydoo

## Can Anybody Find Anything But Hot Air in the Climate Bill?

This question is asked sincerely by a lifelong enviro. A supporter of Al Gore. But this bill appears to have been written by the coal companies based on 25 year old ideas, many of which were accepted by G.W. Bush the Moron President.

The whole idea of the market based solution — the cap and trade solution — making a market in pollution permits — maybe having them brokered through a firm like Enron — which I think did actually broker some of these permits for a while — that idea is 25 years old. It is not change. It’s just slapdash legislation based on making the old dregs by bygone ideas look like a new bill by updating the year and putting a new cover on it. It’s like the old news that CBS, NBC, and ABC purvey — stuff from a few weeks ago — offered today as your “news”.

Nobody in America is willing to do any part of their job anymore. It’s a nation of AWOL officials and AWOL staffers and AWOL employees.

If they wanted a real climate bill, they would have included funding for the hydrogen technology. Ways to electrolytically dissociate water efficiently. Ways to store hydrogen efficiently. Ways to burn hydrogen in fuel cells, or in turbines (possibly combined with methane to make hythane (R).

There would have been a huge push for the sorts of thing T. Boone Pickens is recommending. Natural gas powered trains would have been in the mix — and transcontinental tracks for same on the median strips of East West Highways.

Geothermal would have played a huge role. It is a very rich power source in some places, always on, not like solar or wind. Hawaii could power all seaborne freight in the Pacific with Geothermal based Hydrogen Fuel Cell Gas.

Tidal Hydro would have been in the bill.

Micro-scale wind generators (egg-beater style) would have beeb there.

The National Energy Spine (super efficient cable from coast to coast) would have been there. This creates conservation by allowing energy to be wheeled from coast to coast so peak loads can be met with cheap energy on both coasts.

Instead we get the ancient mantra “Let’s find a market based solution (that way G.W. Bush The Moron President, and the Republicans can be happy). No breakthroughs please! No movement away from fossil fuels, and certainly no less coal or oil! We’ll just do this with financial manipulations, sort of Enron style, with pollution permits, create a playground for the K Street lobbyists, make it look like we are doing something because what we do is so complicated administratively.That way we can do nothing — and nobody will know.

With or without cap and trade the carbon footprint of the energy plants was bound to be legislatively reduced in future years. Cap and trade just bring Federal Pre-emption and knocks out the states ability to legislate on this matter. It’s a form of state legal dis-ablement. It’s a form of permission to just keep on keeping on — more of the same.

The climate bill looks like a 100% perfect fraud, from the gitgo. Mr. Axelrod thinks it has a fairly good chance in the Senate because of the writing changes that were made at the last minute in the House, and on this he’s probably right. Coal can see when it has a good deal. The whole issue now will be off the table for the next 10 or 15 years, and there are 10,000 ways that the “caps” can be removed or made more lenient, triggered by all sorts of extremely complex micro-pico-nano regulations that only the coal companies have time to figure out and understand and know how to lobby with. They can get out of the caps. They get a vacation for 15 years. They get out from under state laws. Whee ! … this pollution stuff is easy!

All politicians are politicians. Nature is always Nature. So the Canute story is always apt. The vanity and the lies and the fraud never actually trumps nature, so you can count of on the climate to keep warming up and the CO2 levels to keep going up and the sea level and storm damage to keep going up. If we truly wish to stop being a hypocrite nation, we’ve got to get rid of all politicians. Put a truly independent agency in charge of climate change mitigation — something like the Federal Reserve or the FCC or the NRC — it’s got to be able to make and implement rules smoothly and quickly. It’s got to be run by Chairmen with long terms of office, at least 10 years, 15 would be better. The Chairman has to be mission focused, not politics focused. If can’t get around the Canute Problem (The problem that wise King Canute taught his ministers about based upon knowing that Politics never trumps Nature)., we can’t deal with the climate change issue. This new bill, is just more hot air. Maybe you can find something in it and tell me about what you think is there. Anyhow that’s my question, asked by a true blue enviro, an AlGorista (with rhythm, hence an algorhythm, I’m a poet, I know it, float like a butterfly effect, sting like a karma-effect).
For Dana the Master of Science — I know that H2 is not a mobile source fuel and never will be. For fixed point fuel cells, no problem, especially if mixed as Hythane (H2 + CH4). Here is Gao Bwo Fu, Doctus Juris, Magister Plutus to tell you read my book, “Cost-Effective Ways to Comply with the New Clean Air Act”, or my articles published by Herald-Mail.

H2 is not a fuel for mobile sources, but it’s fine for fixed point sources. If you want conversation why do you block all e-mail so I have to use this question extension to answer you? You can reach me by e-mail real easily, master of science (and where is your 600 page book on the subject of hydrogen burning — cause mine is in the libraries). Never smarty-pants a smarty-pants.

Scepticism is next to Godlicism. I know it.

This science-thinker atheist says, “Bless you, keep those good questions coming!”

Yes. For example, it will help increase fuel efficiency by 25% by 2020.
Http://switchboard.nrdc.org/blogs/paltman/americans_save_on_fuel_bills_u.html

It requires that utilities produce 20% of their energy from renewable sources and increased efficiency by 2020.

It invests \$90 billion in energy efficiency and renewable energy by 2025.

It establishes new standards for building efficiency, requiring new buildings to be 30% more efficient in 2012 and 50% more efficient in 2016.

It directs EPA and the State Department to use 5% of the allowances to secure agreements from developing nations to prevent tropical deforestation.

It’s certainly not a perfect bill, but it’s pretty good, and it’s the best we’re going to get in the forseeable future. Plus it’s much better to have a framework in place which we can improve upon in the future than to have nothing at all.

See the link below for a useful summary.