Abstract:

There are many computer tools for analyzing the integration of renewable and sustainable energy systems [1]. However, for a pedagogical approach it is more convenient to develop a simpler, even if perhaps more limited or less realistic, worksheet-based methodology which allows the students to develop a more in depth and holistic understanding of the relevant variables for the design of a sustainable energy system. Furthermore, experience has shown that this bottom-up, hands-on approach leads to strong motivation of the students, strengthening team work and critical thinking.
In this paper we will describe an example of this type of approach for an introductory course on Sustainable Energy Systems of the MSc in Energy and Environment Engineering at the University of Lisbon. Conceptually, the approach used follows that of Mackay [2] but introducing hour variability, which is essential for a meaningful discussion of the need for storage. The course is based on a one case study for an imaginary island.
The students are asked to develop a fossil free full energy system, including electricity, heat and transportation, for an island of 50,000 people. The only data provided are hourly time series of temperature, precipitation, wind and solar radiation for one year. The case study is developed in 4 successive tasks. First, using the data provided and reasonable assumptions, the students assess the renewable inland and offshore energy resources. This is an appropriate time for the review of renewable energy technologies. The second task deals with energy demand. Using typical load diagrams, heat demand (determined from the temperature time series) and mobility requirements, the students determine the island energy demand. The next step includes a bibliographic review of other essential topics such as transportation of energy (district heating and electricity distribution costs), demand conditioning instruments (demand response, daylight saving, electricity price elasticity, etc) and storage technologies and costs. The final and crucial step is the integration of the whole energy system. It usually starts with a net approach (annual energy demand must be satisfied by annual energy production) and then becomes more sophisticated as hourly variations are taken into consideration. The final design also includes a detailed discussion of other relevant topics such as the need for redundancy for an isolated community, the food vs. biofuels competition for land, the costs and challenges for the energy paradigm shift, or the possible impact of climate change on the robustness of the energy system.
We will describe the methodology for the whole case study and guidelines for in class discussion, illustrated with student results.

References:
[1] D. Connolly et al, A review of computer tools for analyzing the integration of renewable energy into various energy systems, Applied Energy, Volume 87, Issue 4, April 2010, Pages 1059–1082
[2] David J.C. MacKay. Sustainable Energy – without the hot air, UIT Cambridge, 2008. ISBN 978-0-9544529-3-3. Available free online from www.withouthotair.com.