Comparison of different green energy solutions

October 17, 2010 10:39 PM

Comparison of carbon reduction/energy efficiency/ cost-benefit of rain water tanks V solar heating V waste water reclamation?

I'm looking for any way to compare the cost-benefit of water tanks, solar water heating and waste water reclamation over a fairly large development whether by a comparison of the carbon foot-print reduction, possible environmental benefits, a full on cost-benefit analysis or something else of a similar nature. Can anyone offer some guidance on the best way to compare them all on an equal footing? Is there some kind of environmental group or rating system like LEED green building rating which may have information on the subject?

posted by parryb to Technology (4 answers total)

Rain water capture and waste water reclamation would provide more of a benefit in areas with less groundwater or where aquifers are being depleted, or where the groundwater needs to have more contaminants removed to make it safe to drink. since the benefit varies by location, I think you may have a hard time finding a valid global standard to compare their carbon footprint reduction to solar water heating. Even compared in, for instance, one US state, this varies -- at the extreme, areas where water must be hauled tend to have rainwater capture on everything for the monetary cost reduction alone. Additionally, there are similar factors in solar water heating, such as how electricity in generated, local cloud cover, if there are problems with minerals causing maintenance issues, and the varying dollar costs of electricity.

A friend in Environmental Engineering does lifecycle analysis (and consulting) of different options for various things, it also looks at factors such as how long things last before they need to be replaced, if they can be recycled, transportation, and probably several things that I'm forgetting. IANAEnvirEng, if you want hard numbers on this where you can show some solid backing on what the results are you may need a consultant.

If you want to push a particular one of these three in exclusion of the others (although it's not as though they are incompatible, they all seem to show up together), the vendors of the products may have something. If part of the benefit you are looking for is an increased sales price, they may also have some surveys on what public perception of such systems in you area is.
posted by yohko at 1:20 AM on October 18, 2010

Lifecycle analysis, which yohko referred to, is essential. I am constantly surprised at how often apparently intelligent people compare the carbon reduction, energy efficiency etc of various devices (or policies, or whatever) only on the basis of gross "savings" after they are in place and working, ignoring completely the energy and carbon costs of construction, transport, installation etc at the start and replacement, decommissioning etc at the end.

You probably already knew all of that, but considering how many people don't seem to get it I thought I'd emphasise the point.

Anyway, I can't give you any more specific advice but I bet if you contacted the environmental engineering or equivalent department of a uni near you they would know exactly who to talk to (and would probably be happy to help).
posted by A Thousand Baited Hooks at 4:29 AM on October 18, 2010

From a recent engineering grad who has had academic (not real world/project) experience with the LEED system/requirements: If you're looking to really improve the building's impact/footprint/carbon cost/etc over the life of the building LEED is a great place to start and brainstorm for ideas but good old common sense, research, and finding consultants that are vested and care are going to be much more beneficial than simply going for "LEED silver" or some such.

Don't get me wrong, LEED is great at what it does do, which is encourage and direct companies and organizations to improve what they're doing but it is by no means perfect (or even good in some peoples eyes) at saving the environment from detrimental human actions.

Off topic: Economy in design can often have a much larger impact than adding 'features' designed to do X, Y, or Z. Good insulation > Solar Panels in much of the country. Building orientation with energy usage in mind is another example that is often overlooked. /rant
posted by RolandOfEld at 1:30 PM on October 18, 2010

Response by poster: Thank you all very much, great answers. I didn't really think there'd be any way to bring it back to a simple number or star rating without a detailed analysis, especially as it is very dependent on the locale, but i just wanted to make sure I wasn't missing something. Sounds like an environmental engineer is the way to go then. Thanks again for the help
posted by parryb at 2:20 PM on October 18, 2010