Modelling Renewable Energy Integration “A System Dynamics Approach": Case of Tanzania

Abstract

The transition to a sustainable energy system is constrained by two key factors: fossil resource depletion and the rapid adverse effects of CO2 emissions leading to climate change. This thesis uses systems dynamics to model the sustainability index of an energy resource termed “the energy return on energy investment (ERoEI)”. The energy return on energy investment (ERoEI) is a dimensionless metric which defines the ratio of the ‘net useful energy’ return to the society to the energy consumed in the making the ‘net useful energy’ available. We employ the ERoEI to measure the sustainability of fossil and scale unlimited renewable resources (Wind and solar) in Ghana. Considering the dynamic evolution and stochastic behaviour of ERoEI, causal and feedback loops (systems dynamics) are used to model the interactions between the different intervening variables of the two sub systems under investigation: the fossil and the renewable sub system. Furthermore, a timeseries of dynamic evolution of ERoEI is developed for a period of 90 years starting from 2010 to 2100. 2010 is used as the incept year of the fossil fuel technology and as base year from which the modelling process starts and 2100 is considered as an end period of the modelling process. The approach consists of evaluating for each sub system two key attributes termed the technological progression and the resource quality. The technology progression for fossils in Ghana is considerably faster than renewables but the rate at which the fossils degrade is also very high leading. The combined ERoEI for fossils (natural gas and oil) grows gradually from 2010 with a value of 1 and peaks at a 2026 with a value of 15. 2026 therefore corresponds to the year of maximum fossil production in Ghana, however, after 2026, the fossil ERoEI drops gradually as the ultimately recoverable resources continue to decrease until the value of ERoEI drops below 1 by 2040 indicating the fossil resources no longer yield net positive energy to the society. Unlike fossils, renewables begin with a relatively low ERoEI, a value which is practically zero as there exist no significant renewable energy plants in Ghana now. However, our model shows if the government of Ghana continues to develop renewables, the ERoEI of renewables will grow steadily from 0 in 2020 to a value of 15 by 2030 and this value is maintained until the end of the simulation period 2100. By a simple comparative assessment of the ERoEI of the two sub systems, it is more appropriate for the government of Ghana to plan integration of renewables as quick as possible as fossil resource depletion is eminent as from 2026. Therefore, renewables are the better energy resource for the Ghanaian economy looking at the value of the ERoEI and the technical potentials of the resources available unlike fossils which are on the rise but will soon deplete.