Geothermal Energy

Geothermal energy is another one of those renewables that seems like a no-brainer. Cut your heating bill in half or more? Sure, sign me up. True, the mess and expense of installation is a major hassle. But if you can afford the initial costs and don't mind your yard looking like a nightmare for a little while, it's cheap, efficient, and environmentally friendly.

My family lives on a fairly large property -- ten acres, mostly paddock for horses. So if I can ever pitch the idea successfully to my parents (maybe when the economy improves a bit) geothermal's certainly a viable option for us. As the speaker from Earth River Geothermal said, essentially if they can get the drilling rig into your yard, you're probably a candidate. But in urban and suburban areas, this may be less of an option. Rows of townhouses with little postage-stamp yards could certainly benefit from geothermal just as much as houses on larger plots -- probably even more so, given effects of population density -- so I wanted to take a look at the options for them.

A Canadian company claims that they can get a direct exchange geothermal pump even into small lots. They use copper pipe rather than plastic for better energy transfer, and drill only down to 30 meters; the article doesn't say specifically, but I would guess that this is how they can deal with smaller lots, perhaps the drilling machine and area needed aren't as large as they would be for a deeper hole? However, I wonder about how long these systems last. The speaker mentioned that the material for the pipes was selected for durability, so that the system would last for decades once installed. Copper's fairly durable as well, but this seems to indicate that it works better under some conditions than others. So they have the potential to be as durable, but soil conditions are important to consider to reduce risk of corrosion.

Landfill Energy

According to the EPA, "As of December 2007, approximately 445 landfill gas (LFG) energy projects were operational in the United States. These 445 projects generate approximately 11 billion kilowatt-hours of electricity per year."

11 billion. And that's only 445 projects out of the 3,091 active landfills and 10,000 older landfills in the US. Well, we have to keep in mind that not all of the landfills are going to be ideal methane producers -- some of the older ones are dead, and conditions may be wrong in the newer ones. The EPA estimates another 535 "present attractive opportunities" -- but that's still doubling the number currently in existence. And if that's only counting the attractive opportunities, as the technology improves less attractive ones may become usable as well.

What's more, since methane (the gas that is collected and used for landfill energy) is a greenhouse gas more potent than carbon dioxide, burning it not only provides an energy source but also reduces climate impact of landfills.

However, there are a few technical difficulties with landfill energy. For instance, overestimating the rate of landfill gas recovery can lead to economic problems later, especially with operating costs and the issue of how long the new facility will take to pay for itself. There are also problems with level of demand for power and how well the system interconnects with the existing grid. Overall, however, landfill energy looks like a way to get some environmental and energy return on what would otherwise be just a bunch of trash.

More on electric cars

Some more thoughts on electric cars...

I posted last week that creating "recharge stations" would extend the distance an electric car can travel. But now that I think about it, I'm not so sure. The difference isn't just swapping out gas for electric -- charging a battery takes more time than filling a tank. How much time? Well, it depends on the battery. But think about how long it takes to charge your computer, or your iPod, or your phone -- several hours. It's possible to "speed charge" a battery, but it will ultimately decrease the battery life, damaging the battery. So unless electric car owners are prepared to spend three hours at a rest stop or similar waiting for their car to charge, road trips are out of the question.

Perhaps a solution would be for electric car owners to carry a spare battery and exchange it out when one gets low, the way that some people swap out laptop batteries or similar. However, then we run into the problem of size and weight. Where are you going to fit that spare battery? The Roadster has a system of 6800 cells, each about the size of a AA battery, all adding up to about 450kg. That's not the sort of thing you can cart around in your trunk and swap out at will.

Not to mention that all rechargeable batteries gradually wear out over time, their life slowly decreasing until ultimately they will no longer hold a charge and must be replaced.

It makes sense, if you think about it. Consider: my laptop (a relatively new machine) has a lithium-ion battery rated at 85WHr. It's about the general size of my forearm, and rather heavy. Compare that to 53kWh -- that's KILOwatts, a thousand times greater -- on the Tesla Roadster. Now, obviously we're comparing apples and oranges a bit here, but if the technology existed to make large batteries tiny safely and at an affordable price, wouldn't that have expanded into the field of portable electronics? You can't get more bang for your buck, so to speak, not with current technology.

And lithium-ion batteries, while they offer good performance, run the risk of thermal runaway. Remember on the news a while ago, that recall on Dell batteries? Because they were CATCHING FIRE?

(image from geekologie.com)

Yeah. That.

Obviously not going to happen with electric cars -- we hope. Tesla Motors, at least, has considered the problem and acted pre-emptively to make sure they're safe. But it goes to show you. Nothing's free when it comes to energy: try to make a smaller, more powerful battery, and you produce more heat. Faster charging may mean you have to replace the battery sooner. New technology costs money, and that cost will carry on to the consumer. But if we don't switch to an alternate fuel for our vehicles, we'll just keep burning through gasoline until there's none left. There is no solution that does not require a trade.

The question is, what are we willing to trade?

The Tesla Roadster

After today's class, I decided it'd be worth it to do a little more math to investigate the Tesla Roadster. Their site features a lot of information on performance and efficiency, but out of curiosity, I wanted to be able to compare the efficiency side-by-side with standard and hybrid cars currently existing. The site claims that the Roadster can go 220 miles between charges. From the worksheet we got in class, I got the figures of 53 kWh stored in the battery in a single charge, and 1 gallon of gasoline = 132 megajoules of energy. From there:

1 Watt = 1 Joule/second, so 1 J = 1 W*s, or 1 kJ = 1 kW*s

(22o miles/53 kWh)*(1 hr/60 min)*(1 min/60 sec)*(1 kW*s/1 kJ)*(1000 kJ/1 MJ)*(132 MJ/1 gallon gas)

= 152.2 miles/gallon

Now, it's possible that my unit conversion is rusty. But that seemingly astronomical number seems consistent with numbers given by other electric cars. Aptera goes a step farther, claiming the equivalent of 300 miles per gallon. And while it's true that electric cars can only run as far as their battery charge will allow, the 220 mile figure on the Roadster still allows for 110 miles out and back -- more than enough for the vast majority of car trips. Given support, recharge stations could be built that would make electric cars viable for even longer trips.

What I'm wondering is, where's the catch?