MyHomeYourHome/Elements of the Home/Energy Sources
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Goals for the home's energy
We aim to develop a set of reliable, low-impact, sustainable sources of energy for the home. The resident's participation in the energy sources of the home seems like a good idea, because it makes the user more aware of their usage. Good? Bad?
- what energy sources can be used?
- is it important to use multiple energy sources?
- how can we keep costs of building and maintaining multiple energy sources low?
- can these systems be intuitive/ transparent enough for the user to self-maintain them?
Kenneth and Tim from Queens University were kind enough to break down for us some of the potential energy sources for the home, and related issues. Thanks guys!
Here are a few things that Tim and I discussed a few days ago. All the topics below discuss energy methods and their specifications. There are a few other topics that were discussed, but I will email that out later.
Would you be able to provide me a bit more information on the climate, etc. that this will be used in? Thanks!
We looked at Geothermal, Hydro, Wind, Biomass, Photothermal and Photovoltaic.
Geothermal and Hydro
To begin with, Geothermal and Hydro are great sources of energy, but they require installing pipes. Geothermal would require that you create a complete circuit so that air flows through the pipes underground and back up. This will help reduce heating costs, etc. As for Hydro, running a pipe from a large body of water underneath the house and back to the large body of water would help moderate the temperature of the house as well. Geothermal pipes would have to be below the frost layer, while the hydro pipes would be closer to the surface. However, there is one major issue with this: this would require property of the land since we would be modifying it. As such, these two options are not feasible. Rainfall can also become a source of power. By setting up a rain collector above the house, it is possible to collect a sufficient amount of water so that its weight can run a turbine. You can hold water in a container and let it travel through the turbine to you by releasing a valve when there is sufficient quantities of water. This is possible, but it depends on the quantity of rain that there is in the area.
Wind is a common method to generate electricity. General rule is if you want something to generate more electricity make it taller and make it larger. Due to the property issue brought up with geothermal and hydro, the wind turbine would have to be attached to the house or small enough that it can be taken on and off. Attaching it to the house brings up two issues: structural support and noise. The structure in question would have to be small, so that it can actually be supported on the house. Furthermore, if it was small, it would generate a lot of noise which would not be appreciated in the environment. There are actually laws restricting height and noise levels of wind turbines in Canada. I highly doubt that this will be an issue though. In the scenario that we do not attach it to the house, it would be fairly close to the house and would not generate enough energy to warrant it. This may be an option if you need a constant mechanical energy.
Biomass was briefly mentioned, but due to the actual quantity of it, it is not possible to generate a sufficient amount of energy from it.
In terms of solar energy, two options were discussed: Photothermal and Photovoltaic cells. Photothermal would be the most efficient way of capturing solar energy. To make a simple photothermal cell, one would run water up through pipes on the roof which would then run back to the inside of the house. Normally you create a closed loop and just let convection heat the house or make it touch a water tank, so that heated water can be used. To make it efficient, one would use copper pipes, paint everything black and tightly seal the area. From what I gathered from the climate though, it won't be of that much use. Photovoltaic is the other option. The obvious method is to mount cells to the roof of the house. Another option is to attach awnings to the house, most likely above the windows, with Photovoltaics mounted to them. Lastly, you can also get windows that have cells built onto the window so that it generates electricity. You can find more information on them here (http://www.xsunx.com/Default.aspx). For specifics of cells, you'd most likely want mono crystalline silicon cells, because they're better terrestrially unless you use a concentrator system. Silicons power generating capabilities decrease with an increase in temperature, but clouds don't decrease its output as much. Therefore it will still generate electricity even in semi-cloudy conditions. Mind you, there is a high financial investment with cells.
We considered two main options for the roof: Photovoltaic and extensive green roof. Photothermal didn't seem that beneficial, so it isn't discussed, but I can go into it if you want. Photovoltaic cells on a roof would provide a fairly consistent source of energy. Meanwhile, green roofs save energy through temperature management. It reduces the heat island effect, and provides a barrier between the roof and outside. Green roofs are also supposed to help extend the lifespan of a roof. Beyond the house owners, photovoltaic cells don't really help the community. Green roofs help the community by reducing storm water runoff. Storm water runoff frequently costs the government tons of money, since the system can't handle the extra water. From an environmental standpoint, photovoltaics aren't that environmentally friendly. They amount of energy and elements that are used to create them is incredible. They are also harder to setup. Meanwhile, green roofs are easier to set up and manage -- at least extensive ones. By extensive I mean ones that are, for example, a simple layer of grass. This is not limited to a layer of grass though. You can also try growing really light vegetables for food. When it comes down to it, it depends what you want. From a purely environmental standpoint, green roofs are better. But if you need the energy, photovoltaic cells are better. Furthermore, the heat retention of green roofs can be reproduced by increasing insulation within the house.
Most if not all of the energy that you harness will be in the form of electricity, so you will need to store it somewhere. The standard batteries are Lithium ion polymers, which are frequently used in laptops. However, if you plan to use a Lithium battery, you might want to check out Lithium iron phosphates. I recall them being more environmentally friendly. Avoid Lithium ion batteries though, since they non-rechargeable. The main issues with Lithium-based batteries are that they're horrible for the environment and that they're highly explosive. If you opt for Lithium-based batteries, get them pre-assembled with battery protection built-in. If you don't, it will be a hassle to assemble them -- they are very sensitive to temperature, current, etc. Beyond that, you can also use nickel metal hydride batteries. They are heavier but less reactive. There's also the option of deep cell marine batteries. I'm not that familiar with the specifications on the batteries though. One interesting idea is using an organic battery. A professor in Taiwan came up with a chlorophyll battery. It basically runs on sunlight and any form of liquid. It might be an interesting idea for the outside of the house. It was created last year, so I'm not sure if you can get them yet, but they have a low production cost. Here's an article on it (http://www.worldchanging.com/archives/008971.html).
If you choose to use raw cells you will need to put them together. A few things to keep in mind with that: use soldering paste to connect them. Normally cells are attached using tabbing and soldering it, but I've seen people use soldering paste, which you just toss in the oven. It's a lot easier to work with and you will break less cells with them. Cells are very fragile, especially the cheaper ones, so expect to break some. If you're running it to a battery, you may need a peak power tracker. For solar car, we ran mono-crystalline silicon cells and triple junction GaAS to Lithium ion polymer cells and we needed to use a peak power tracker. What a peak power tracker does is keeps the voltage at a certain point, so that it doesn't fluctuate as much. I'm not sure if it was specially used with the Lithium ion polymers because they are really sensitive, but you may not need one for other types of batteries. I'm pretty sure it wouldn't matter if you ran it to, for example, a lead acid battery.
If you mount photovoltaic cells onto the roof, you will need to protect them. One possibility is to put a sheet of plastic that is parallel to the photovoltaic array, but that is a few cm above the array. This allows for the array to remain cool while protecting it. This will have to be developed more for future use though.
Ideas surrounding the use of human power in the home have come up a few times. Examples include those little hand-cranked camping lights, or a bike powered generator. We're looking into the feasibility of these sources.
- Would residents be willing to contribute their own energy?
- How much energy can be produced, and what percentage of needs would that serve?