What Do You Want To Power ?
With any off-grid power system, careful
selection of the devices to be powered can massively reduce the size
and cost of the system required to power them. Efficient devices often
make all the difference to the
viability of a project.
To demonstate how dramatic these savings can be, listed below
is a simplified comparison of two ways to acheive the same overall
goal. One scenario costs almost 10x as much to power as the other.
For the purposes of this example - let us assume that each
device needs to run for 5 hrs per day in winter in the UK - imagine a
very small off-grid home office.
|Example Office - Scenario 1 - Normal Mains Appliances
Example Office - Scenario 2 - Highly Efficient
Desktop PC @ 100w x 5hrs = 500 whrs
Laptop PC @ 20w x 5 hrs = 100 whrs
A/B Class Stereo Amplifier @ 25w x 5hrs = 125
Digital Class Amplifier @ 3w x 5 hrs = 15
Incandescent 100w Light x 5hrs =
CFL Light Bulb @ 18w x 5 hrs = 90
Total per day = 1125
whrs + 20% Inverter Losses.
Total per day = 205
whrs (+ no inverter losses if devices are DC).
The difference in the costs to power these two simple scenarios is
huge, Scenario 2 will cost about 10% or 15% of the cost of Scenario 1.
The first scenario would require approx 6x the size of solar array,
battery bank, cabling, support structure, delivery & installation
costs ... as well as an inverter.
Therefore you can see why it is so important to select high efficiency
devices. As shown in the example
above, with careful planning, this is where you can save
serious money on the cost of a remote power system.
To make these high efficiency devices easier to source, we now
offer some of the more
ultra-efficient dc lighting, audio and ventilation equipment in our product range.
How Much Power Does It Use ?
It is important to take the time to establish how much power
each device uses. Most mains devices can be easily tested using a
simple, low cost, plug-in
The power figure from the energy label on the back of the device or the
manufacturers specification sheet is often peak power, which is
normally far higher than the average. Conversely, many mains powered
devices draw power even when they are supposedly 'switched off'.
Testing smaller DC powered devices may need a multi-meter or the
manufacturer may be able to supply some data for average power use. Our
experienced system design team can help if you get stuck here - we have
figures for many appliances.
When Does It Need To Run ?
To minimise running times throughout the system, use timers,
PIR motion sensors and well designed controls with
your appliances. These
convenient devices offer huge opportunities to reduce energy
Recently a new type of energy saving multi-plug has appeared on the
market. These 'smartplugs' shut down multiple devices based on one. For
example, when a PC is turned off ... the printer, scanner, speakers and
possibly network equipment is all automatically shut down as well.
On small off-grid power systems we recommend trying to avoid the need
for an inverter to be running 24/7. All inverters use power on standby
also loose power in conversion from DC to AC. Therefore DC lighting,
fridges, freezers and IT equipment all cost less to power from DC.
How Critical Is The Supply ?
What are the consequences of running low on power ? Critical
systems tend to be designed with a higher spare capacity. This can also
be supplemented with a larger battery bank and the entire system can be
backed up by a diesel generator.
A well designed off-grid solar or wind energy system, correctly
installed, is highly reliable. Maintenance involves an occasional clean
of the solar panels and checking of batteries, with very occasional
change of bearings on a wind turbine.
With modern technology - it is even possible to send a text or phone
warning alert if a critical system is running low on power, thus
enabling preventative action. Online system status web pages are also