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The problem with generators
The traditional method of
generation for small scale electrical supply is the diesel generating set.
These are reliable, give a good
quality electrical output, give the required power whenever it is required , and the
capital cost per kW installed capacity is fairly low.
However, they have the drawbacks of
being:
- dirty
- inefficient
- noisy
- expensive to run
- requiring considerable maintenance
All these problems are exacerbated
under low-load conditions.
Batteries with a generator
The addition of a battery
store and battery charger/inverter will give immediate benefit to almost all situations
where a generator is used - avoiding, for instance, a 7.5 kVA generator running late at
night to run a TV and a light bulb - giving increased efficiency and lower running costs.
Including a wind turbine and/or
photovoltaic panels for the battery charging can then replace diesel running time further.
See details of
Outback,
Studer &
Sunny Island
Inverter/charger units, which are ideally suited for these
applications.
In typical domestic situations, for
most of the day, loads are very small - perhaps a few lights and other appliances.
For a small proportion of the time,
however, large loads such as washing machines, electric kettles, etc. must be powered.
Sizing a renewable energy system to
meet this peak demand is, in most cases, prohibitively expensive (at least initially).
Consequently, the optimum way to incorporate a wind and solar energy is for these to
supply the low loads required for most of the day, and allow the diesel to start up
automatically to meet the small proportion of loads for which a large capacity is
required.
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Systems
 In
typical remote home situations, for most of the day loads are very
small, perhaps a few lights and other small appliances. For a proportion
of the time, however, larger loads such as washing machines, electric
kettles, etc. must be powered.
Sizing a
renewable energy system to meet this peak demand is, in most cases,
prohibitively expensive (at least initially). Consequently, the optimum
way to incorporate wind and solar energy is to allow these to supply the
low loads which are required for most of the day, and allow the diesel
generator to power the smaller proportion of heavy loads for which a
large capacity is required and to act as back-up battery charging.
Several
levels of system are possible depending on load requirements and
available local wind/solar resources.
These all incorporate a
battery store which is charged by any spare capacity whilst the generator is running and
by the wind generator &/or PV panels.
Selected
loads can then be run from this battery store either directly using low
voltage DC appliances and circuits, or via an inverter using existing
230Vac wiring and appliances. Generator use can then be restricted to
periods of high demand; to power heavy loads; and to recharge the
batteries in times of low wind or sun.
Together,
these measures minimise the running time of the generator, let it work
near full capacity and give 24 hours availability, avoiding, say,
starting it for 5 mins. or so to switch on a light, which in the long
run can lead to high maintenance costs.
To spread
costs a phased approach can be adopted, with first the addition of the
diesel support system and then later the wind generator or PV’s to
charge the battery. Smaller systems can be enlarged if needs change by
addition of a larger battery store or inverter etc..
Working it out
In deciding upon an optimum
system, the best approach is to evaluate the existing pattern of electricity usage
including wattages of appliances, periods of use etc., together with priorities for
improvement.
Energy efficiency measures such as
using gas for cooking, better fridges, and use of low energy bulbs for lighting, all help
make a system simpler and cheaper.
Wind & Sun can offer a
range of services to help in choosing an appropriate system, including installation.
Please write or email including details of
power requirements, existing power supplies and information about the site such as local
wind and solar conditions, map and plan etc.
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