The Value of the NegaWatt
I had a lovely phone chat last evening with a young lady, a high school senior who was working on a paper for school and wanted to ask a few questions about solar energy. In particular, she wanted to know the cost of converting her entire town (Arcadia, CA — 56,000 people, let’s say 20,000 households) to 100% solar.
Understandably, she hadn’t thought through some of the implications. E.g., you’re contemplating cutting these homes off from the grid and replacing that service (the cost of which is quite low, as it’s shared across literally millions of homes) with the cost of individual PV arrays and battery storage that would provide each of these 20,000 homes with reliable power.
“OK,” I suggested, “Let’s do the math and answer your question. Let’s assume these are your typically 2000 square foot homes; I would guess that the per-home cost for PV with full storage/back-up would be about $20,000. Times 20,000 homes is $400 million. That’s a lot of money for one small community. Who’s going to pay for that?”
This is what you’d be forced to do if you were building a house in the middle of nowhere, with no access to an electrical utility. But since each of these houses is already grid-connected, a less radical approach would be adding PV for daytime use, selling excess power back to the grid, and using the grid for power at night.
I went on to explain that I view renewable energy as the “next best thing.” The very best thing is not using the energy in the first place. A staggering amount of electrical energy would be saved if everyone living in each of those 20,000 houses would wear sweaters in the winter instead of cranking up the heat, open the windows in the summer instead of blasting the air-conditioning, replace incandescent lights with CFLs (and turn them off when not in use), insulate pipes, ceilings and walls, etc.
She seemed to be absorbing this nicely. I hope she did well on her paper.
Some utilities charge more at peak times, like late afternoon in the summer. A PV system that is sized just under your maximum daytime load will be able to reduce the demand on the grid at peak times. You won’t make a lot of money selling electricity to the utility grid anyway. Net metering isn’t designed to be a big money maker, just a way to pay you to not be a drain on the grid supply. A smaller PV system is cheaper than a complete, self contained system with storage.
Another way to use solar is for heating. Solar water heating is very cost effective. In winter, solar thermal systems can provide a lot of heat for the money. This will also reduce demand on the utility supply.
Consider that many electric grids are WINTER PEAKING, like where I am in Kentucky, like most northern US states, like all of Canada. In winter-peaking electric utility territories, peak electric demand and usage is most often very early winter mornings. I called an engineer at my utility and asked. Its peak is BEFORE SUNRISE. In winter-peaking utility zones (a huge amount of the developed world) there is much stronger argument for at least some storage with PVs. Also, the Duke Energy system just north of me in northern KY and SW Ohio is summer-peaking but peak occurs from 11am to 8pm. There’s a prof in New York writing abt this, saying grid-tied PV systems designed for peak abatement should face southwest. This puts the peak output of PVs in better sync with typical east-USA utility peaks which are more similar to Duke-Ohio than simply surrounding solar noon. That prof recommends at least a few hours of battery storage.
Well said John.
There are however other options than batteries.
These options include
Managing hydro-power resources as a swing producer
Introduction where possible of pumped hydro storage facilities
Interconnection of winter and summer peaking power grids by long distance high voltage direct current power lines (In this regard, Europe is far more interconnected than the USA and Canada)
Incorporation of more wind power in winter peaking regions (winds are often stronger in winter)
Load shifting – use of devices such as ground source heat pumps and immersion heaters off peak to store heat for use when required rather than for direct heating drawing power when heat is required
Greater utilization of district heating and resources such as solid biomass to displace heating loads currently met by electricity.
I’d be happy to open the windows more often if it didn’t create a dust problem.
In places with little dust where the nights are cool, a whole house fan can work well. Just open a few windows in the evening and turn on the fan, and cool outside are enters through all the open windows, even when there is no wind outside.
Evaporative cooling might be considered as an alternative to air conditioning if you live in a low humidity area. LED lighting will save even more energy than compact fluorescent, and other small measures like “shower head” inserts in the faucets can greatly reduce both water and energy use as much of the water they save would have been heated.
One more thing, don’t forget to improve the insulation and to ensure that you have appropriate shading of windows in summer (External blinds or shutters are ideal). This will reduce both summer air conditioning and winter heating loads.
Whether you are on or off grid, taking the above measures wherever possible will be sure to save you more money than they cost lowering your overall cost of owning / running your home.
My previous house had evaporative cooling and it worked reasonably well. There is even significant room for improvement in evaporative cooling technology. Fortunately, the huge fires east of here didn’t occur until after I moved into my new house which has vapor compression cooling, otherwise I would have had to do without cooling in extremely hot weather since the evaporative cooling system would have blown the smoke into the house.
The difference in efficiency between LED lighting and fluorescent lighting is fairly small. Also, compact fluorescent lamps are less efficient than the classical fluorescent tubes. Although CFLs do have their place, I do not understand why fluorescent tubes are ignored. The lighting in my new house was designed around fluorescent tubes rather than CFLs for two reasons: Tubes are more efficient, and they can provide more even lighting. They also have a longer life.
Correction: I should have written “west of here” instead of “east of here.”
Craig,
On this issue we completely agree. In the same manner that new demand will always result in an increase of 100% fossil energy, demand destruction will always result in a DEcrease of 100% fossil energy. If you have baseload demand destruction you’d see 100% of the energy reduced come from coal, if you had daytime demand destruction you’d have most of the energy reduced be from natural gas…
But all of the energy reduced will be fossil sourced.
However, I strongly disagree with your price assessment for most houses. In California you get a great deal of subsidies from both your state government and your local utilities.
For a real-world scenario (outside of California), however, it would cost ~$4/W installed, and the battery pack would cost ~$500/kWh installed. For a 2000 ft2 house, if you were designing a minimum system that would work during December, and you lived outside of Sunny California, you’d want at least an ~8 kW system, and at least 20 kWh of storage (and that’s for a VERY efficient house)… So just there you’re looking at a cost of over $37,000 per house… and that’s essentially a fairy-tale level of efficiency.
The true cost for a non-grid tied 200-home pure solar community would be over a billion dollars before you considered the commercial and industrial needs.