Designing Ecological Habitats - Gaia Education

170 Designing ecological Habitats
even if only for a few weeks a year or few hours a day. The grid can be
this ‘backup’ but the temptation to use it more as a primary source can
compromise good, super-efficient design. On the other hand, it makes no
sense to invest in a lot of lead-acid batteries to be ‘off-grid’ and then use the
grid as an intermittent backup. Better to install robust ‘grid-tie’ solar, wind,
hydro, and/or Stirling systems and use the grid as your ‘battery’.
If you are fully off-grid, when your renewable sources are not meeting
your needs or when your batteries are empty, the use of a backup generator
becomes essential. You can use a relatively silent natural gas or propane
powered Stirling generator or your can use an internal combustion
generator running on natural gas, propane, agriculturally produced green
gas, hydrogen, or biodiesel.
Whole System Design
Okay, so now it’s time to put it all together into an integrated design package.
Again, it’s best to consult a professional – but the more homework and
design practice you do yourself, the easier the process will be for everyone.
Energy Budget
For all buildings and sources you’ll need an energy budget. How many
kWhs per day, per month, and per year will each building require? This is a
critical figure and often one of the most difficult to obtain – but do it! There
is no substitute for this accounting; without it you are guessing on design.
Use a detailed “load spreadsheet” that lists just about every light bulb and
end-use you have, determining the watt-hours per day and hence per month
of each. Do this for Winter and for Summer. You won’t regret it.
Also characterize your source potentials in detail: solar surveys, hydro
surveys, waste-heat and wind surveys. How many kWhs/day or month can
you rely on from these sources? Don’t skimp on this process either. Quantify it!
Location of Sources and Uses
Map the location of your community’s buildings and other power-users as well
as all your potential source sites. Critical design decisions in terms of distance
and degree of centralization depend on it. Characterize the sources and loads
on the map so you know how much power comes from each and goes to where.
Which buildings could hold solar panels? Is there a place for a ground- or polemount
solar system? For hydro or wind, where are optimum turbine sites? And
don’t forget to mark future expansion possibilities on the map.
Decentralize or Centralize?
Creating your own electrical ‘mini-grid’ with a central meter may be a better