Modelling and Analysis of Distributed Energy Systems with Respect to Sustainable Energy : Focus on Electric Drive Vehicles

Abstract

Climate change and CO2 emissions is an important issue on the agenda of many politicians. Trying to decrease CO2 emissions, influences transportation, power production, etc. The power system is characterised by an increasing amount of renewables, with one of the most expanding renewable power sources being wind. Wind energy is fluctuating by nature, calling for increasing flexibility elsewhere in the energy system. For Denmark, hydro power from Norway help stabilizing the system, as does export of excess wind to Germany, although the latter is decreasing in use because of large correlations between high wind production in northern Germany and western Denmark. To decrease CO2 emissions through a decrease in the use of fossil fuelled plants, along with an increase the amount of renewable energy, the power system needs more flexibility such as flexible demands, storage etc. Flexibility could also come from the road transport system. Counting for 24% of the CO2 emissions in Denmark in 2009, the road transport system needs to move towards, e.g. electric drive vehicles. However, the electric drive vehicles are also demanding electricity from the power system. This brings both challenges and opportunities to the power system. One challenge is, that intelligence is needed unless peak-load is to increase drastically. With intelligent charging of the vehicles, though, the electric drive vehicles can be of great benefit providing flexible demand and charging at night time, instead of being regarded as yet another load and challenge for the energy system. Furthermore, discharging of vehicles can provide services to the power system. The batteries in the electric drive vehicles are batteries invested in anyway. Hence, why not use these actively for cheap storage by the energy system? Furthermore, the use of vehicles are opposite to the remaining demand for energy; e.g. while people are making dinner their vehicles will often be parked, being able to deliver back-up power - again, a great opportunity for the power system. In this PhD project I have focussed on modelling and analysis of a future integrated transport and power system. An integrated power and transport system enables analyses of the interactions between different parts of the energy system. The object of interest is an optimal configuration of an integrated power and transport system as well as I will be focussing on the drawbacks and benefits for the power system incorporating an electrified transport system. I have performed analyses in terms of integrating more renewable energy, for both Denmark as an isolated system and for the northern European countries including Denmark, Sweden, Norway, Finland, and Germany. The analyses are performed using the deterministic energy systems analysis model, Balmorel. Furthermore, analyses have been made for the Irish power system on the influence of introducing electric drive vehicles in a predefined power system, using the stochastic energy systems analysis model, Wilmar. Interesting is, that it turns out to be most profitable to invest in enough wind to more than cover the electrified transport in Denmark. This holds, both when modelling Denmark as an isolated country, and when including the interactions between the Nordic countries. Furthermore, analyses show that fuel cell electric vehicles are not yet ready for competing with the other vehicle types. This is, among other things, due the technologies not being cheap enough, thus, the development is not expected to have reached a competitive stage. Another interesting finding is the results showing that it is beneficial for Ireland to have electric drive vehicles in terms of both costs and CO2 emissions. However, introducing the electric drive vehicles in Ireland, imply an increase in both costs and CO2 in the Great British side, as most of the power for the vehicles is produced on British coal power plants. Thus, focusing nationally, Ireland should invest in the electric drive vehicles, although, on an international level, the investments are costly.