Saturday, March 10, 2007

Electricity Inefficient for Heating

Most people think of all energy as equivalent. In reality, there are higher and lower orders of energy, and understanding the difference is key to making the best alternative energy decisions. Energy in the form of work, such as pushing your car or running an electric motor is a higher order of energy than for heating purposes.

As a result, engines which create the work from heat, whether they be turbines, steam,, gasoline or diesel engines operate at low efficiencies. Generally, these engines work at maximum theoretical efficiencies of around 40%. Ultimately, after friction and other mechanical inefficiencies are considered, the efficiencies of this type equipment are generally much lower.

This makes sense when you think about it. Taking your car as an example... you know that a significant amount of the energy in your fuel is dumped to atmosphere as heat from your radiator and exhaust. In fact, about one third of the energy in the fuel is discharged in each of these areas.

So what does this have to do with electricity? Your electricity is generated by some type of engine. So, the efficiency is necessarily less than 40%. In fact, when mechanical and electrical losses are considered, efficiencies are likely in the 30% range. This is ok when it is used for higher order work, since you would have these inefficiencies even if you generated the power on site. But for direct heat, your efficiencies are well under half what they would be if you generated the heat, a lower order energy, directly with the fuel. This is the reason an electrical water heater is, by definition, considerably more expensive to operate than a gas or oil fired heater. The same applies to your clothes drier.

So, can anything be done about it? The answer is no, concerning the basic comcept. This is a fact resulting from thermodynamic laws. However there are some ways to avoid the negative effect, which may help you in thinking about your energy usage:
  • Use fuels or heat sources directly whenever possible for heating. Gas, oil or solar are all preferable to electricity if available. This concept is the reason heating from solar is much more efficient than using photovolataics or electricity for the same purpose.
  • Use a heat pump. Heat pumps, as the name implies, do not create heat directly, they pump the heat from a lower temperature to a higher temperature. As long as the temperature differences are not to high, the efficiency of the heat pump makes up for the inefficiencies inherent in generating electricity. And, heat pumps, by virtue of the pump effect, create cooling in the location from which the energy is pumped, as well as warmth on the warm side, so they can create both cooling and heat in the same process. In this era of high energy costs, increased use of heat pumps for water heating can significantly decrease energy use over direct electrical heating.
  • Cogeneration. Where there is a need for both power and heat at the same location, they can be connected to significantly increase efficiencies. Cogeneration is being increasingly used in the process industry. If a plant, or nearby plants, have a need for heat, they can use the waste heat from the engine while generating power or electricity, thereby substantially improving efficiency from below 40% to over 90%. Cogeneration is well established in process plants, so why can't it be used at home? In theory, it can. Homes require both heat and work. The problems lie in economies of scale and the lack of low cost, reliable, efficient small engines. And, begging for some good use for their waste heat...your automobile.

So, hopefully, you have a better understanding of energy use and efficiency basics that will help with identifying and selecting energy investments.

Friday, March 09, 2007

Economics of Green Energy

Jon makes some great points (see comments on a previous post) about how energy alternatives need to be driven by both economics and environment.

As mentioned, oil sands are significantly dirtier that conventional oil and gas. Take a look at the yahoo financial site of Sunoco (SU), a significant oil sands producer. There you will see discussion of new projects to mine and process oil sands. Both the mining and processing require significant amounts of energy be expended, resulting in increased pollution. And the disruption to the earth and waste products will be significantly higher than for conventional oil and gas. You'll also see much discussion about reducing the environmental impacts, but regardless, the environmental impact will be significant. Others, including BP and Occidental, have experimented with "in-situ" processes, meaning the process takes place in the reservoir itself, by injecting either steam for heating or injecting air to allow underground combustion. The heat introduced into the reservoir helps separate the oil from the sand and makes it flow so that it can be extracted. In my mind, this process is cleaner, resulting in less disruption and waste disposal issues, but the additional energy, and resulting pollution, is still needed.

Beyond oil sands, it is an unfortunate fact that many of the energy alternatives that have potential for a significant effect on energy supplies (nuclear, coal) in the near term have different, but significant negative potential environmental impacts. I would even argue that some of the greener alternatives have largely unrecognized negative impacts. I still remember when nuclear energy was considered the solution to all our environmental problems. This was just a few decades before the industry was run out of business by environmental interests.

And, that brings us to the intersection of economics and environment. Traditionally, environmental issues have not been directly driven by economics, although the issues do often intersect. Traditionally, governments set environmental regulations based on the philosophy in power at the location and time. Then, businesses decide whether it is economic to improve the operation to meet the regulations, and if not, they get out of the business. Many will argue that this is good, but to the extent that the most economic processes are forced out, or the costs are passed on to the customer, our standard of living is negatively effected. And, when it comes right down to it, few will make that tradeoff.

Economics and the environment also meet at the customer. If customers value the environment, they can influence business to change operating practices or to shutdown offending operations by refusing to buy from the offending business. Again, however, the result is a decreased standard of living. Customers and businesses make these decisions daily and with little guidance, and the operations ultimately reflect the preponderance of these decisions.

There have been some efforts to more formally connect the environment and economics by use of a pollutant or carbon trading system. The theory is that such a system will drive the most economic solution to reducing pollution by encouraging those who can most economically reduce pollution and allowing those who have the most difficulty in reducing pollution to buy credits. This would address one of the biggest difficulties in managing pollution, ie deciding who should reduce pollution and by how much to reach the most economic solution. Both governments and consumers are consistently poor at managing this process, equivalent to a doctor trying to make delicate incisions with an axe and little knowledge of where the incision should optimally be placed.

Unfortunately, in practice, pollution trading systems have not been very effective. Since only governments have the power to adopt the system in a mandatory way, the system has been largely voluntary. The result is that those who could easily reduce pollution are eager to do it and sell the credits, but those for whom reductions are more difficult can just ignore the system. Therefore, those who voluntarily use the system are at a competitive disadvantage unless their customers are willing to pay a premium for a green process. Oops, you are back to whatever the customer demands, right where you started.

BP has used the system with limited success internally. By setting a "Value of Carbon" price and using this in the economic model for alternative evaluation they can at least see where reductions in greenhouse gases within their operation make the most sense and track the effect of their projects on greenhouse gases.

The above sounds like gloom and doom, but there is a bright spot that should be discussed. Economics and the environment often are aligned by the intersection between them. When you do something to decrease your energy use driven by economics, you also reduce pollution. When you buy a compact flourescent light bulb, it is both a good economic decision and a reducer of pollution. The same applies to almost all demand reducing projects. This often applies for supply-side projects as well. The additional energy demands for oil sands drive both worse economics and more pollution than for conventional oil and gas. That is why most oil sands are still in the ground, and will stay there as long as there are adequate conventional sources.

Obviously, economics and the environment require a balance, but tools to effectively manage this balance are pretty crude. The question is whether these decisions will be made accurately and soon enough. This is a difficult question to answer, since the effects of today's decisions can be long lasting. And, our understanding of the compensating mechanisms nature may have at her command are even less precise than the tools discussed above. Ultimately, though, I believe the actions will be taken in time, largely because of my faith in the ability of nature to adapt to circumstances. And, when the system gets far enough out of balance, it will be obvious to customers and governments the decisions they must make. That is not to say that the adjustments will not be painful, but I don't believe they will be disastrous in the big picture.

One further point. You mentioned "forcing" companies to change. While this is appropriate in terms of economic and other forces creating change by exerting pressures in various directions, I think it often reflects a basic misunderstanding of the nature of business that is prevalent (and destructive) in today's society. Companies are not monolithic structures independent or opposed to people. They are made up of individuals just like their customers, making decisions based on their incentives, their values, their understanding, just as you and I are. I think it is important, and rare, that we recognize this commonality is much greater than our differences, and that we communicate with and educate each other. This alone can help us resolve our problems in the most efficient way.

Tuesday, March 06, 2007

Cooling by solar heat from attic

Ok, I promised a diagram of how you could cool your house using heat from the attic. So, I've worked up the rough schematic below to help explain how it might work.

There could be a number of variations of this basic concept, but I hope this will do to explain the basics.

Start with adding a styrofoam sheet to the bottom of your rafters on the south side and a baffle to trap the hot air at the peak of the roof, as shown in red. This increases the temperature of the air at the peak and helps create a draft effect to move the air upwards. Then, again shown in red, add a chimney which has a warm section on the south side and a cool section on the north. Again, this adds to the temperature and draft effect of the hot air exiting the attic. A downward draft effect is also created in the north half of the chimney for cool air.

Cool the air in the north half of the chimney by blowing through an exchanger with a swamp cooler. Alternatively, it could be cooled by circulating water through the ground or rerouting the cool air outlet from the bottom of the cool half of the chimney. For arid regions, more temperate climates or for the shoulder season, this would likely create all the air conditioning required. Unfortunately, most air conditioning demand is in more humid climates and in the peak season, and that is where your solar heat comes in.

By adding a slowly rotating desiccant wheel at the top of the chimney, you can remove humidity from the air entering the cool side. This will warm the air, but this heat can easily be removed by your swamp cooler exhanger. So, below the desiccant wheel and swamp cooler you will have dry, cool (approximately 80 degrees) air. By misting at this point, you can reduce the air and water temperature further, to approximately 55-65 degrees depending on the condition and characteristics of the desiccant. The desiccant is then regenerated (ie, the moisture is removed) by the hot air on the warm side of the chimney.

The cool air and water generated in this way can be circulated through exchangers to cool the house. Alternatively, the cool air from the chimney could be introduced directly to the house, although this would require opening the windows slightly and might result in too much humidity in the house as with a traditional swamp cooler.

Side benefits include a cooler attic since the drafting effect and baffles remove the heat from the main part of the attic. Air conditioning by this method should reduce power usage by 75-90%. At the same time, I believe this system could be installed for less than the cost of a traditional central heating system.