The CPSL trial site was designed to enhance the performance of microgeneration on-site renewable energy production whilst substantially reducing the cost of grid connection and easing the current demands on
the high voltage grid network during times of high production and low demand, due to the growth in embedded generation from grid tied renewable sources. Concentrating on the renewable sector of 15kW -
250kW production, in the main CPSL found that these were agricultural and commercial single applications, the system will work equally well in single, split and three phase installations.
CPSL have completed an installation at a trial site in Cheshire incorporating a 48kWp PV system and a 20kW wind turbine at a location with a 6.0m/s average wind speed. CPSL found that the power generated, prior to the Clean Power Solution, is often not at the times of demand. Additionally, although not in this instance, the installations are usually in remote rural settings with poor grid connection resulting in a costly
transformer upgrade. CPSL therefore took a different approach to most renewable companies and firstly examined the annual use of the site in both electricity and heat demand and then matched the production accordingly. This negates the need for a grid upgrade as there will be no export above 16amps per
phase, which is currently allowed under engineering recommendation G83/2.
For example a 20kW wind turbine installed at a location with a 6.5m/s average wind speed will produce approximately 72,000kW of generated power per annum. The power generated however, is often not at the times of demand and so surplus electricity is exported to the grid at say 4.5p per kWh. When the farm needs to use electricity, it will often buy it
back at a much higher price than what it has been paid by a power company for its export.
Principle of Design
Production is measured by an energy management system (Emma) along with the demand from the batteries at any time by two current transducers located in the circuit. The electricity demand in the property
is met from the renewables and supported by batteries via a synthetic grid. The voltage transducer records the battery condition and signals Emma. When the batteries reach 90% charged, export at 16a begins via a G83/2
certificated inverter and remains until the batteries drop to 80% due to lack of wind. If the batteries drop below 20% (in times of low wind for more than a day) power is drawn from the grid to recharge the batteries back to 50% capacity. When the batteries are at 90% and exporting, power is sent, via SSR’s in 3kW bytes to the electrolyser. The electrolyser produces, from rainwater
using 5kW of generated power, 2.1 Kg of hydrogen per day, this is stored in the hydrogen tank at 30bar pressure for use in a Giacomini hydrogen boiler when required.
Summary
By adopting this system the site demands are fully met in terms of electricity and heat by the renewable generation and the hydrogen, when used, it is a carbon free heating solution. The number of electrolysers and
hydrogen storage facility can be multiplied up as required, with each using 5kW maximum when available.
For systems larger than 50kW, CPSL have instructed a South Wales Company to begin development of a combined heat and power unit using a carbon free hydrogen powered three cylinder internal combustion
engine to drive a generator. The system cost will often be met or significantly contributed towards by the saving in grid connection upgrades whilst the consumer has no requirement for imported power or heat to their site and places no additional strain on the UK high voltage
network.