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...renewable energy systems
(1) Small Stand-Alone DC System
Typically used
- on remote buildings to power lighting and low consumption appliances or in situations where an existing battery based system is in place eg. vehicles, boats & caravans.
- to run small dedicated loads eg. remote lighting, telemetry or monitoring equipment.
To be successful, efficient use of the electricity generated is essential and the system must be sized to meet worst case conditions.
(2) Stand-alone AC/DC Systems
This
system is the same as (1) with the addition of a DC to AC inverter to enable the use of commonly available 230Vac appliances.
This enables a very wide variety of equipment to be used. To ensure reliable system operation, the inverter should be carefully matched to the loads so that it is capable of running everything that is needed. Usually a larger wind generator, PV array and battery store will be required than in (1) because electrical requirements will be higher. Circuits for both low voltage DC and conventional 230Vac loads are required.
(3) Stand-alone AC Systems
Here all the loads are run on AC using an inverter to convert power stored in the battery bank to 230Vac.
This simplifies wiring since low cost, readily available cable, switches, outlets and fittings can be used. Good wind/solar resources are important in order for the energy demand to be satisfied even when weather conditions are poor and the renewables must be sized so they are able to put sufficient power into the batteries to maintain demand at all times. The inverter must be sized to meet the maximum electrical load that is needed ie. to run all appliances that might be on at the same time. Usually fuels other than electricity are used for heating & cooking.
(4) Wind & Solar with Back-up Generator
This can be an economical alternative to a large
stand-alone system, since it does not have to be sized for worst case weather
conditions. A petrol, LPG, or diesel generating set combined with a battery charger can supply power if the batteries become low. The generator can also power peak loads, giving savings in inverter cost and allowing a smaller battery bank to be used. Often for places without any mains electricity a generator will be the existing source of power so adding a battery store with inverter/charger and additional wind and/or solar generation is the perfect way to reduce fuel costs and to make 24hr a day power available without running the generator all the time.
(5) Wind Heating Systems
Here the bulk of the output from the wind turbine is used for heating and various heaters can be switched in or out depending on the power available.
Whenever it is windy power is provided for loads such as water or space heating. Power can also be made available for normal use via a battery and inverter to run conventional 230Vac electrical loads. Because heating loads need to be powerful to be useful (usually several kW) then this type of system is only possible using large wind turbines and for locations with good wind resources. Heat pumps can be incorporated to maximise heating potential of the electricity generated. Solar electrical heating systems are not viable simply because most heating is usually needed in the winter when there is least sunshine available.
(6) Grid Interface
This is used in a grid connected house which wants to place less reliance on the grid. A battery/inverter system provides some or all of the power.
If the battery becomes low or loads exceed inverter capacity the transfer switch can be used to connect the house loads to the mains - this transfer can be automatic. This type of system can be increased incrementally, thereby reducing dependence on the grid. It can provide the perfect back-up power system for situations where there is an unreliable or expensive grid electrical supply.
(7) Grid Connect Systems
Where the mains is available instead of surplus power being stored in batteries arrays
of photovoltaic modules and wind turbines can be connected into normal household
consumer units simply by means of special synchronous inverters, - allowing any
home or business to generate power from renewable sources. Power generated is first used within the property to reduce electricity consumption and any surplus is exported to the grid. Various schemes and tariffs are available through electricity suppliers to enable credits or payments to be obtained for both generated and exported power.
In addition to the normal Import kWh meter which measures electricity consumed an
Export kWh meter may be required to measure the surplus and a Production kWh
meter enables electricity generated to be measured. Often the lower price paid
for electricity sold compared to electricity bought makes it advantageous to
make best use of all power generated, for example by using electricity during
periods of high generation.
Note that if the grid supply fails, to protect linesmen working on the grid the system will shut down,
so these cannot be regarded as a standby source of electricity.
For more information see Projects
(8) Grid Connect Systems with Battery Back-up
These are the ultimate renewable energy systems and give complete energy independence!
They allow all the convenience of mains electricity but with reduced bills due to on-site renewable electricity generation and also provide emergency long-term back-up power in the event that the grid fails.
Power generated by wind and solar power is used by household loads and any surplus is used to charge a battery bank, once this battery is fully charged further surplus energy is exported to the grid and a credit or payment can be obtained for this. If the grid goes down the battery/inverter system takes over to power critical loads and wind or solar electricity is still generated to maintain the charge in the battery.
Systems can be can be easily expanded. Back up power can be added to existing grid-connected systems and additional wind or solar generation can be added.These systems provide future-proof energy autonomy and allow a home or office to be generate clean electricity, maintain uninterrupted power and save on energy bills.
System protection is included to ensure that all regulations are complied with.
(9) ISLAND POWER Systems
Applications include:
Village power supplies Island power supplies
Hotels &mountain resorts
Remote farms
Lodges & Cabins
Hospitals &Schools
Telecommunication and radio stations
Mobile applications
At present, approximately 1.6 billion people are living without a regular electricity supply, the effects of which include stagnant development and increasing poverty. Many remote areas with scarcely populated areas are without power because connecting them to centralised power would be uneconomical. Many of these locations are ideally suited to benefit from the integration of renewable energy: wind; solar and water power - systems are now possible to allow self-sufficient communities to generate their own electricity from their local resources Because of distances involved the easiest way to design such systems is to connect the various sources of energy and consumers via a common AC bus. This enables an off-grid to create it’s own local grid which can be easily extended to power additional properties or allow the integration of new renewable generation. Generation can be sited at the most appropriate locations and power delivered across long distances to properties as it is needed. Both single and three phase network systems are possible together with systems incorporating medium voltage transmission to enable power to be distributed over large distances to electrify an entire neighbourhood.
For more information on remote island systems see projects on Foula, Flatholm and Eigg or Sunny Island Inverters and Sunny Island Models
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