31 Mar 2013

The third part of sustainable energy

When we talk of sustainable energy, a lot of us think of generating electricity from natural energy sources like solar or wind. Or we may think of using fossil fuel-based energy more efficiently. But there are also many ways in which we can use natural resources to substitute for electricity, whether renewable or not. This matters because conversion of natural resources to electricity has a low efficiency.

Here's a partial list. The surprising thing for me is that there are so many opportunities:

- Solar hot water, rather than electric or gas-fired heaters. This is a no-brainer in tropical countries with abundant (too much, in fact) sun. But we can go beyond using solar hot water for bathing, also using it for running washing machines (rather than electrically heating the water), and for cooking, as well rather than heating it using gas or electricity. This requires all water to be potable, but that's something that's old hat in developed countries, so there's no reason we can't do that in India.

- Solar air-conditioning. Most air-conditioners work by using a compressor, which consumes huge amount of energy. An alternative is to use the heat of the sun as a substitute. It's counter-intuitive, but you can use heat to cool a room.

- Ceiling-level windows. These are windows that are located just below the ceiling, rather than at the normal height. Imagine a one-foot-high window that stretches from one end of the wall to the other. You can have them on all sides of the room that are exposed to the outside. Since hotter air in a room rises to the top, these ceiling-level windows let the hot air leave the room, keeping it cool, resulting in lower air-conditioning bills (not to mention more comfort for people who can't afford air-conditioners to begin with).

- A similar idea is a window on the roof. Obviously it's feasible only on the top floors of buildings, and need to be water-tight (lest the rain come in). These provide both ventilation and light, perhaps letting us avoid turning on artificial lighting for a little longer in the evening.

- Windcatchers, which literally catch the wind or breeze blowing above your house and directs it into your house. These can work like a funnel, effectively forcing the breeze into your house. In some designs, the wind blows through a small container of water, working as an air cooler but for your entire house. This can be more efficient than an air-conditioner. Why confine ourselves in closed houses and then complain that it's too hot?

- Heat-reflective paint on roofs and walls, claimed to reduce temperature by a few degrees. I don't know how well they work.

- Solar panels, in addition to generating electricity, absorb some of the heat from the sun, cooling your house. If this logic is right, it should be accounted for in the calculation of the price of solar energy — solar energy may be cheaper than it is widely considered to be if you account for reduced air-conditioning bills.

- Solar cookers, though I don't know how well they work.

- Triple insulated glazed windows which consists of three layers of glass, sealed with argon or krypton gas, to keep out heat and noise. This reduces air-conditioning bills. It's silly to spend a lot of energy cooling a room only to have the heat seep in again through the windows.

- Bathrooms can have big windows so that they dry without needing an exhaust fan powered by electricity. For privacy, you can close the windows.

- A cool roof, which is made of a material that reflects up to 80% of the energy falling on it. Less efficient is a green roof.

- A radiant barrier, which is placed below the ceiling in a room, and reduces the heat coming in.

- City-wide walk and cycle ways, which should be open to other forms of self-powered transport like roller skates. Even if you take public transport, that still uses a non-zero amount of energy, as compared to walking. Not to mention that you keep fit this way. We also need cycleways since you can cycle farther than you can walk.

We need elevated walkways where space is scarce and the street too crowded and polluted (both gases, dust and noise). And perhaps underground walkways in tropical countries — no one wants to walk in the 45-degree heat.

- Rainwater harvesting, rather than pumping water in over hundreds of kilometers, which is not as efficient as collecting the water right at the point of use. On the same note, we should use low flush toilets, taps and shower heads, and reuse gray water, which is water generated from activities like washing clothes or bathing, not sewage or human waste.

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