Rethinking energy
 

i wont post the articles but just the url. cosmos features this week are all about energy.

http://www.cosmosmagazine.com/featur...-scale-storage

Rethinking energy: Wind, solar and storage

http://www.cosmosmagazine.com/smart-cities-energy

Rethinking energy: Smart urbanisation

http://www.cosmosmagazine.com/featur...ovoltaic-cells

Rethinking energy: Organic solar cells for off-grid use

http://www.cosmosmagazine.com/featur...nuclear-energy

Rethinking energy: Advanced nuclear

Any comments on the contents?

not by me. i just put them up for anyone who is interested.

Regarding the first one, I always wondered why mechanical storage wasn't considered. Something that pushed water uphill, or compresses air, etc and can release it later would surely be cheaper than a battery to produce and install and increase in capacity? Maybe even almost as efficient as a battery in terms of the energy recovered.

Has it ever been seriously considered?

Well, pumping water back uphill for later use is used in the Snowy Hydro Scheme. That was pretty serious, and quite a while ago now.

As boxhead said, pumped storage has been around for years. It's also used in the UK, I remeber visiting a recently completed pumped storage scheme there about 45 years ago.

The main problems are that it needs a huge quantity of water and a substantial height difference to store a significant amount of energy, and the capital cost is high.

Still, I'm sure we will see more of it in the future as it's probably the most efficient way of using excess energy from wind and solar and the like.

Yes, it is done commercially in large scale systems and it works very well. There are numerous pumped storage systems around the world.

On a smaller scale, there are some problems. The first is that you need two tanks, or perhaps dams. My 300 watt solar pump will hoist up around 15000 litres of water per day against about 15 metres of head. That might represent 1.5 kwh. From this, I might be able to get 1 kWh back from a turbine. So lets multiply this by 3 as a minimum to provide 3kWh per day (which is about what I use). Then allow another factor of say 5 to allow for dull days. So now I need two tanks of size 15,000 * 15 = 225,000 litres. That matches those large water tanks that you often see in rural homes. The cost however is going to be perhaps $25k (I think). That is before you buy the turbine and pump that would be needed. By comparison, my batteries cost $9000. The life of the tanks might exceed that of the batteries I suppose. I am not sure how long the tanks would last.

The second issue is following the load demand. Turbines are not instantaneous. So you would need to use a battery bank to allow you to follow the load demand. A small battery bank perhaps, but batteries none the less. And of course an inverter.

Thankyou all, I admit I assumed these types of systems were not in commercial use going by the tone of the article.

And I was surprised by the results of your calculation as well morrie, cheers. I intuitively believed that batteries would carry a higher capital cost.

Capital cost for water storage *could* be less if you just happen to have the right geopgraphy.

Morrie, what capacity for $9000 of batteries?

I think we should use solar energy to vapourise sea water, then use existing landforms and wind patterns to condense the water vapour, and collect it in large natural tanks by placing artificial barriers at the end of existing valleys.

The greens will never go for it.

I seem to remember being involved in the construction of one of those some years back. Only difference, we placed the artificial barrier just downstream of a lake discharge, raising the river level to that of the lake.

6 x Enersun 1320s Martin.

Thats a grand dream, but you know what they say...

1320 ah
4v

5280 whr

Six of them


Over 30000 whr
30 kwhr


So about double the water system you mentioned?

Did I get the maths right?

The design was for 10 times the daily demand, so yes, that does sound correct. But that is a nominal capacity only.

...barriers at the end of existing valleys. concrete? is that all you think of?

;-)

I've been using about 10 Megajoules of electricity per day to heat this room during winter I'm wondering if using petrol might be less expensive.

Yes, pumped hydro is common place and compressed air storage and flywheel energy storage are two others in development, though i am not sure about their deployment.

Though using storage for tradition generation is the norm as you want to buy cheap (at night when baseload generators would rather sell cheap than shut down), then sell when the price as high (during peak periods).

If there is good geography for pumped hydro, it is probably already there.