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Comment by TeMPOraL | Hacker News Reader

> Thus solar and wind fit in with our natural rhythm quite nicely.

It's not that nice, because power output from wind/solar plants is random (depends on things like cloud cover or wind strength) and it causes problems in power grid, where power demand must meet the supply exactly, or bad things will happen.

"Without Hot Air"[1] covers this, and other renewable-related issues quite nicely and with real data. I recommend it, it's a good read. It has some good ideas on how to solve power supply/demand problems.

On TED2012 there was a talk about a new kind of batteries designed to solve those kind of problems in the power grid; the video from the talk is not yet up, though (but I think it should be soon, at [2]).

[1] - http://www.inference.phy.cam.ac.uk/withouthotair/

[2] - http://www.ted.com/talks?lang=en&event=2012&duration...

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power output from wind/solar plants is random (depends on things like cloud cover ...) and it causes problems in power grid, where power demand must meet the supply exactly

The biggest power cost for us in warmer climates is cooling. When the sun is out, we need lots of power; when it's not, not so much. Solar power sufficient to run A/C from rooftop panels costing less than grid electricity would be wonderful, lining up perfectly with the inconsistencies of available sunlight.

Especially if one would switch to heat pumps, which can do both heating and cooling, providing/removing 3 to 5 times more heat than electricity they use up to do so. Amazing technology, by the way :).

Most air conditioners are heat pumps configured to work in one direction, using outside air as a temperature sink.

(I realize that this is at least borderline pedantry)

Oh, I interpreted A/C as Active Current; my mistake. Thanks for pointing that out.

(I, for one, don't mind pedantry :))

I would start with better home design and energy efficiency enhancing improvements before throwing a Carnot-limited solution at the problem.

Last summer I ran an experiment. We live in a two story house in California. We usually see low temperatures at night (sub 70deg F) and highs in the range of 105+ degF during the day. At night I opened all of the windows downstairs and used a small industrial fan (about 2000CFM) to pump cold outside air into the house. In the morning I'd shut down the fan and close all windows.

I could get the lower part of the house down to below 70F on most days during the summer. Cold enough to have to wear a sweater. Even with the outside temperature hitting highs above 105+ the thermal mass of the house succeeded in maintaining a very comfortable inside temperature (max around 77F). We did not use the air conditioner at all last summer, saving tons of money. The fan costs pennies a day to run.

This summer I am looking at what efficiency improvements I can make to this arrangement. I'm itching to throw a micro-controller at it, but I want to learn a little more before I take that path. There's a lot to do in the roof. Think about it, you have this huge solar heat collector --the roof-- reaching ridiculous temperatures during the day and radiating that right into the house. Sure, there's attic insulation, but that's a ton of energy to deal with.

I'm thinking that some forced ventilation of the attic with a small fan might just do wonders.

>I'm thinking that some forced ventilation of the attic with a small fan might just do wonders.

Radiative barriers should also be on your list. It's essentially just mylar stapled to the rafters.

That only works in desert type environments (i.e. little to no cloud cover) where the temperature goes up and down each day.

Where I live if it gets hot it says hot, day and night. And most of the country is the same.

Although, obviously, incremental improvements are great even if only some people can use them.

You might be able to use the thermal stability you have underground to help cool the house. Granted, this is more expensive, but probably far less costly in the long run. The basic idea is to bury a heat exchanger (coils of tubing) deep underground and circulate a fluid to move heat from hot to cold.

You can use this two ways: You can use it to try to cool the house directly by embedding tubing in the floor/walls or some other approach. Or, you could use it to improve the efficiency of an air conditioning unit by providing supplemental cooling of the A/C unit heat exchanger coils.

When solar and wind power input is not meeting demand that seems like a good time to spin up the spare fossil fuel generators, at least as a transitional sort of thing. Maybe in the near future excess wind / solar power can be stored as chemical fuel, and burned during peak usage.

An 80% / 90 % cut in fossil fuel usage or higher would be a huge thing though!

Whilst on a small scale they are very random, there are some good studies (sadly I don't have the references with me) that show that over large areas, they actually become quite predictable - so this is less of an issue than people think if you have enough coverage

I meant that it is nice in the coarse pattern. And yes, as said, we need ways to store energy and a flexible grid.

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