EVALUACIÓN DE LAS OFERTAS ECONÓMICAS

The increase in efficiency of distributed CHP over conventional generation can result in a reduction in emissions. The carbon intensity of national grid in 2013 was 0.527 kg / kWh [127] but the carbon intensity for summer 2017 was 0.35156 kg CO2/ kWh. The changing in the amount of national grid carbon intensity has resulted from demand reduction (e.g. LED lightbulbs) and the increase in centralised grid renewables especially onshore and offshore wind. In this thesis, the modelling used an average of five years of carbon intensity which is 0.439 kg / kWh for the national grid in the UK. While the carbon intensity generated by burning natural gas is 0.185 kg / kWh. In practice the

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national grid carbon intensity is not constant, as at different times of year and the day each type of power generation is utilised to perform different functions for the grid. For example, hydro stations have the ability to store energy and generate with a, high bandwidth, i.e. fast response and are also low carbon, but are relatively expensive and usually kept in reserve for sudden changes in supply or demand or to dynamically fine-tune network frequency and power balance. Coal plants are best to have low bandwidth and thus are slower to respond. They are cheaper than hydro stations but have one of the high carbon emissions in the UK power generation mix. Traditionally, coal plants provide additional winter baseloads. Combined cycle gas turbines (CCGT) lie somewhere between, being responsive enough to follow demand under normal conditions and having lower carbon emissions than coal, but still low cost enough for bulk generation. Nuclear plants have ability to respond and cannot follow demand, so they are used world-wide for baseload generation. As a consequence: The generation is a mix of all generators performing the different functions combined. This results in:

• The fuel mix and associated carbon emissions is therefore variable

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• In the UK in 2016, DEFRA put the annual target for average carbon

value attributed to electrical power supply and use of 1kWh of electricity as 0.4kgCO2e/kWh.

There are many other approaches which could be added to any LES to increase energy efficiency and reduce the amount of Greenhouse Emissions (GHE) and operational costs; for example, the reduction of energy consumption. A reduction in energy consumption is defined as using less energy to provide the same service. This results in fewer electrical losses, less CO2 emissions and a reduction in costs. The Committee for Climate Change (CCC) has estimated that a reduction in energy consumption and subsequent energy demand could save 17 million Tonne of CO2 per year [20].

Many non-domestic buildings can reduce up to 25% [20] of their demands on energy by following some simple steps:

• Reduce heating and cooling energy demands to the lowest

levels for any building by increasing building insulation and installing high quality, double glazed windows.

• The use of efficient and low powered equipment and

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with LED lighting and using IT and ICT (information and communication technology) equipment.

• Improve ventilation and cooling systems.

Another approach is to add local renewable energy (RWE) sources including wind energy (RWE) to the LES system to further reduce CO2 emissions. RWE and LES for residential households could reduce CO2 emission by between 21-62%, depending on the type and scale of RWE [21]:

➢ Effective RWE is not limited to creating positive environmental

impacts it also affects the economy by reducing operational costs. An addition, wind turbine or PV do not need fuel, but may require regular maintenance. There are different types of renewable energy sources of various size and energy production capacity. Regarding LES, there are two popular types which are widely used because they are easy to install and use: Wind energy (WE):

Wind generator systems convert wind energy into electrical power. WE is one of several promising and efficient types of RWE sources especially when it is integrated with CHP technology. This combination increases its efficiency and reliability by filling an energy

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gap and reducing electrical energy demands, while reducing overall operational costs. Wind energy reduces total costs by up to 20% by supplying electricity using wind turbines [22].

➢ Photovoltaics (PV):

This type of technology works to convert sunlight into electricity. PV technology is useful not only for the generation of electrical power but also solar thermal power generation for heating or cooling [26]. PV panels are found to operate up to 75-80% efficiency and supply more than 25% of the electrical power demands in addition to 55% of thermal energy leading to a reduction in operational costs by approximately 30% [23,24].

The use of RWE, however presents challenges and has limitations. They are dependent on the weather and so cannot guarantee to work all the time. Windy or cloudy weather will reduce PV efficiency by up to 50%. In addition, all RES systems require maintenance to keep them working properly. For example, the PV panels may require periodic inspection for physical damage, dirt over it or proper tightness and the wind turbine

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need same checking and testing plus checking the electrical connections and inverters.

Finally, one of the biggest technical challenges is integrating the (RWE) with (LES) is maintenance supply of demand matching while reducing the power curtailment especially unexpected curtailment. [25].