User manual

Science Manual – Using Video Images for Fisheries Monitoring 11
3.2 Power supply
3.2.1 Mains power
If mains power can be installed at the site, this is the best option. If the site is at risk
of flooding, the voltage will need to be dropped to 24 or 48 volts AC. This can be
done at the power take-off point (above the flood prone area) and a cable run down
to the site and terminated with an IP68 rated connector.
3.2.2 Battery banks
If mains power is not possible, do not despair. Short-term, and in some cases full-
time, monitoring can be achieved using banks of ‘leisure batteries’ of 85 amp hours
(Ah) or more. These can be used as a stand-alone power source (Figure 3.2) or
connected to a solar panel, micro-hydropower turbine or fuel cell for recharging,
which will extend the time between battery changes.
Solar panels and wind turbines may be appropriate for some sites, but at others
environmental conditions may render them unsuitable. The likelihood of vandalism
or theft should always be a consideration.
At sites prone to vandalism, a methanol fuel cell can be used as this can be locked in
a vandal-proof cabinet. A 30-litre fuel cell, at a cost of £1,810, is capable of providing
100 Ah of energy per day and can provide up to 2,000 Ah before requiring refuelling.
Regular visits to top up the methanol will be necessary, but these will be far less
frequent than for a stand-alone battery system. This may be the only method which
produces enough power for a site with light panels or an infrared LED illuminator
(Section 3.3).
For sites with a lower power requirement, a mini-hydropower turbine may be suitable
although this was not used for this project. The turbine will only work in fast flowing
streams, so will not be suitable for all sites. It can provide a maximum of eight amps
continuously,
The limited power from one or more of the above will dominate the choice of
equipment, with low-power options favoured over higher specification components.
Basically, work out your power budget and remember to take account of power loss
over long cable runs. If you have assumed the least power hungry components and
• MAINS POWER SUPPLY
• BATTERY BANKS
Stand alone
Solar panels
Fuel cells
Micro-hydropower turbines