Power stations can be classified as either centralised or embedded. Centralised power stations are typically large (> 100MW), distant from the consumer and connected to high voltage transmission lines. The electricity they produce is passed along the transmission lines to the distribution networks, and then on to the consumer. This is currently the dominant method of electricity production, and as such is the one for which the system has been optimised. Embedded power stations are typically smaller, located closer to the consumer and connected to the lower voltage distribution network. The governments target is for 10% of electricity to be generated from renewable sources by 2010, with an aspiration of 20% by 2020. Much of this renewable generation could be embedded. Embedded generation can have a beneficial effect on a network, such as loss reduction, reactive power generation and the deferral of re-enforcement to the grid, but the penetration of embedded generation is limited by a number of factors. These include technical, regulatory and economic factors. The technical factors are grid related and include, among others, the effect on voltage control, frequency control, short circuit currents and system islanding. The intermittent nature of some renewable sources limits their benefits to the grid and as their penetration increases, affects the ability of the grid to balance supply and demand. Most of the government’s targets are expected be met by wind power which is inherently intermittent. Solar, biomass, wave and tidal energy, all of which are intermittent, are expected to make contributions at some stage. Energy storage can help with voltage control by shifting generation from periods with low loads to those with high loads. This avoids the need to curtail output. Small amounts of storage can counteract short term variations in the renewable source, whilst larger storage can reduce the effect of longer variations in the renewable source. Barton and Infield used a probabilistic method to show that the use of energy storage with embedded renewable generation does allow more energy to be exported to the grid. This study aims to analyse and model how the use of hydrogen generation by means of the electrolysis of water can increase the penetration of renewable embedded energy generation into the system. It will investigate and critically evaluate the role of renewable-hydrogen power plants in overcoming the technical constraints of grid connection by using stored hydrogen as a balancing mechanism. It will also investigate and evaluate the benefits of the generation of hydrogen for use as a transport fuel, and other high value uses, with regards to a possible future hydrogen economy. In particular it will consider the interaction between the use of hydrogen as a balancing mechanism and its use in a hydrogen economy. It will include within this the issues affecting remote generation, whereby hydrogen is generated at the renewable-hydrogen plant and transported to the point of use, and local generation, whereby hydrogen is generated at the point of use, using electricity from the grid. |
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