Tuesday, November 24, 2009

Penetration of Solar Power without Storage

I'll preface this post by saying that it's a plug for my own research, but it's also published so (at least some people think) that I'm not making it up. Since the work is published in a journal, normally I wouldn't be able to just link to it, due to access limitations, as Fat Knowledge has lamented. However, some professor at a university in Texas has made it part of his course, so I'm going to direct you there for the whole article:

Solar Power without Storage
The idea is that while solar panels are expensive on their own, if you need to build a storage system to use their energy at night, they become even less affordable. Clearly, solar power can't provide all of our electricity needs if we skip the storage, but they can still help out in the daytime. In fact, in most parts of the country, the electrical demand is already highest when the sun is out, so solar can help with these peaks. The higher daytime demand is currently met by turning on "dispatchable" power sources that are (relatively) inexpensive to build, cost a lot to run, and can be turned on and off in very little time. The ones that run less frequently cost less to build (by design) but even more to run, since they won't be generating very much. In fact, the plants that run to fill the demand during the highest 30 or so hours of the year can cost 5-10 times as much (/kWh) as your typical coal or nuclear plant. (The reason that coal and nukes don't produce all the electricity is that these "baseload" plants can take half a week to start up and shut down, and could never respond to the daily variations of demand.)

My goal is to see how much solar capacity can be installed so that the panels mainly replace the dispatchable plants. Specifically, what is the maximum deployment that permits 95% of the annual output from PV to be utilized without reducing the output of the baseload plants? I used hourly solar intensity and electrical demand data from 32 regions across the country to accomplish this.

This map shows the regions and their possible penetration. Note that the share is in effect a measure of the correlation between electrical use and sunlight, and not of the amount of sunlight. Locations with large amounts of sunlight in times of low demand, such as noon in winter or anytime in the spring or fall, will have a lower possible deployment. In this sense, New England’s grey days in October and November help improve the matching because the clouds
reduce sunlight when the electricity use is lowest.

My total installed possible capacity in the 32 regions is 59 GW. These regions cumulatively consume 30% of America's electricity, so if panels are as effective in the rest of the country, the whole US could use 196 GW. This would reduce the energy currently provided by dispatchable power plants by 23% and would represent over 7% of the present total annual electrical load in the US. Although that share may not seem like a lot, it requires nearly 8 doublings from the 865MW of PV which was the installed base in the US in 2007, showing that in the near future, bringing down the cost of the panels is more important than worrying about the dark.

Saturday, November 14, 2009

Personal Carbon Trading

Yesterday I saw Yael Parag from Oxford University present on a plan the UK is looking at for "personal carbon trading" (Oxford description here). The UK, like lots of cities and countries, has all these grand plans for 30% reduction in Greenhouse gases by 2030 and 80% by 2050, but no real plans to accomplish this, and minimal progress. This cap-and-trade type of idea might be able to accomplish the goals. Here is how I understand the plan from the talk:

The UK is generating some amount CO2 each year. Of this, 40% is directly used by individuals in the form of non-business transportation, home heating, and home electricity. The rest is used by commerce, industry, and agriculture for similar purposes, plus manufacturing.

The presenter mentioned, though I can't find any reference of this on the website, that the 60% would be auctioned out to all non-individual users.

More interestingly, the 40% would be distributed evenly among all people. Each person would then have some monthly (or yearly) balance of Carbon. Whenever people buy things that actually produce CO2 when used, they enter their Carbon card number, and their account is debited. An important point is that there wouldn't be that many of these transaction, since the only things counted would be
  • Gasoline/diesel
  • Monthly heating bill (gas/oil)
  • Monthly electric bill
  • Air travel
The carbon credits could of course be bought and sold, and I bet eBay would just be the beginning. I can see entire companies emerging to manage, loan, invest, and speculate on credits.

Although Fat Knowledge prefers taxes to permits (and in general I do too), there are a few points that speak in favor of CO2 credits.
  • Energy is a fairly inelastic commodity: that is, the demand is not especially affected by price. In summer 2008, gas prices rose something like 75% from the previous year, but vehicle miles traveled dropped just 5-10%.
  • People respond to social norms. Just like the California electricity users who cut back consumption to be closer to that of their neighbors, Britons may alter their behavior to use closer to what the average citizen uses, for social norm reasons as well as economic.
  • Caps are good for controlling things that should be, well, capped. Taxes are good for things that the government wants to discourage, but doesn't care if a specific amount are used. For instance, the high cigarette tax (in theory) reduces demand, but it doesn't limit the number sold. But if scientists say that the amount of CO2 generation shouldn't increase, it is difficult to estimate what tax level will accomplish this, whereas the cap dictates the amount and lets the demand set the price. And the amount of credits could slowly be ratcheted down to meet that level that the government/scientists believe is sustainable.
The system has the potential to work well. One concern I had was that people would chalk up all the driving they could as "business travel". But if the firms have to bid on carbon pounds, they might not want their employees using them up. And since many of the poor do not drive cars and live in smaller houses/apartments with smaller utility bills, they could earn extra income selling credits, making this a Progressive measure.

Nevertheless, I do have a few things I wonder about.
  • If firms bid on credits, why is air travel counted for personal consumption? Wouldn't that count twice? Or maybe the system is set up so that the airline industry can pass on the credit use to consumers, rather than the cost of auctioned credits.
  • Mass transit is not included (initially) to encourage use rather than cars, and because there is in general far more of these transactions a month, so it would be a pain to have to debit the carbon card every time. Would intercity buses and rail also be exempt, or would they pass on credit consumption like airlines?
  • For electricity, would we use the average CO2/kwh of the entire country, or the local company's portfolio? Would (in the US) hydro-happy Washington's electricity not debit much, but a lot of points would come out for a kWh in King Coal states like Kentucky and West Virginia? And if, as you can do, you pay a premium to guarantee that your electric company buys at least your amount of kWh from Wind or whatever, would that make your electricity free of credits?
  • Should credit allowance be based on the household? Or is the individual better? How should children be counted? Should you be able to merge accounts, so one family member isn't stuck somewhere unable to buy gas while the other has a surplus? And how much would this complicate divorces? (No, those carbon credits should go to me!)
The government still gets some revenue from the non-residential credits permit sales. But this would certainly be much more complicated than a tax. And would people trust the big bad government to have so much control of people? Would it be better if the system was administered by a big bad corporation? Any thoughts?

Friday, November 6, 2009

Losing Weight by Eating Less

The New York Times writes about a study on weight loss. The results: a diet soda is better than a treadmill. Researchers worked with several groups of people and monitored calories burned and weight loss, and found that lots of exercise did not reduce weight by much. The far-more-important factor was the amount of calories consumed.
“The message of our work is really simple,” although not agreeable to hear, Melanson said. “It all comes down to energy balance,” or, as you might have guessed, calories in and calories out. People “are only burning 200 or 300 calories” in a typical 30-minute exercise session, Melanson points out. “You replace that with one bottle of Gatorade.”
There was also an interesting point made about what form the calories you burn come from, depending on the level of exertion.
While high-intensity exercise demands mostly carbohydrate calories (since carbohydrates can quickly reach the bloodstream and, from there, laboring muscles), low-intensity exercise prompts the body to burn at least some stored fat... “Heart rates of between 105 and 134” beats per minute, Carey said, represent the fat-burning zone.
The article does go out to tell about all the other benefits exercise brings, so even if one doesn't lose weight, it's still healthy:
Most [subjects] became notably healthier, increasing their aerobic capacity, decreasing their blood pressure and resting heart rates, and, the authors write, achieving “an acute exercise-induced increase inpositive mo od,” leading the authors to conclude that, “significant and meaningful health benefits can be achieved even in the presence of lower than expected exercise-induced weight loss.”