International Journal of Sustainable Energy Planning and Management Vol. 21 2019 1 1Corresponding author - e-mail: poul@plan.aau.dk International Journal of Sustainable Energy Planning and Management Vol. 21 2019 1–2 ABSTRACT This editorial introduces the 21st volume of the International Journal of Sustainable Energy Planning and Management. This volume present research on overall national energy planning development with a case from Nigeria. This is followed up by a sustainability assessment of nine sample countries. Moving on to the more local scale, potentials and barriers for photo voltaic systems with cases from Germany, Nigeria and Tanzania are presented. Finally, analyses focusing on the spatial dimension of energy system are presented. This last part addresses both the delimitation between rural and city energy systems and how they should combine and the optimal design of district heating systems. 1. Energy planning and sustainability In this volume, Khaleel and Chakrabarti [1] look into the Nigerian energy system and the planning of the development of the energy system. In this study, the authors compare different modelling approaches for projection of energy/electricity demands in the country. Razmjoo[2] investigate Sustainable Energy Develop- ment Index (SEDI) and its application to a set of nine countries – Albania, Bulgaria, Croatia, China, India, Iran, Jordan, Peru and Tunesia. In the work, the countries are evaluated according to technical, economic, social, environmental and institutional sustainability. 2. Photo voltaic systems for energy development Ugulu[3] look into photo voltaic systems, but from a starting point in unreliable grid supply in Nigeria resulting in the majority of urban households having individual fuel-based generator systems. Photo voltaics are falling in price, yet penetration rates are still modest in Nigeria – largely due to high up-front investment costs. Keiner et al. [4] also investigate photo voltaics and residential smart energy systems with autonomous production, conversion and storage systems – including the extent to which electric vehicles may replace stationary batteries. Self-consumption rates are positively affected by electricity storage – but the cost of energy is increased in parallel. Groth [5] address rural electrification in Tanzania – focusing on photo voltaic systems and mini grid systems. Such off-grid mini systems are assessed as being important bridge technologies before interconnection to national power systems. See also the work on rural electrification by Dominguez et al.[6] 3. The geography of energy systems Möller et al. [7] look into the geographical limitation of sustainable energy regions, focusing on the interplay between rural municipalities’ and cities’ energy planning and energy systems development. A recurring theme in many regional energy plans is that rural areas have options that cities do not have. In their analyses, Möller Editorial - International Journal of Sustainable Energy Planning and Management Volume 21 Poul Alberg Østergaard* Department of Planning, Aalborg University, Rendsburggade 14, 9000 Aalborg, Denmark Keywords: Energy planning; Sustainability assessment; Photo voltaic systems; Energy regions; URL: http://dx.doi.org/10.5278/ijsepm.2019.21.1 http://dx.doi.org/10.5278/ijsepm.2019.21.1 2 International Journal of Sustainable Energy Planning and Management Vol. 21 2019 Editorial - International Journal of Sustainable Energy Planning and Management Volume 21 [4] D. Keiner, C. Breyer, M. Sterner, Coupling heat and electricity storage technologies for cost and self-consumption optimised residential PV prosumer systems in Germany, Int. J. Sustain. Energy Plan. Manag. 21 (2019). http://dx.doi.org/10.5278/ ijsepm.2019.21.4 [5] A. Groth, Socio-economic impacts of rural electrification in Tanzania, Int. J. Sustain. Energy Plan. Manag. 21 (2019). http:// dx.doi.org/10.5278/ijsepm.2019.21.6 [6] C. Dominguez, K. Orehounig, J. Carmeliet, Modelling of rural electrical appliances ownership in developing countries to project their electricity demand: A case study of sub-Saharan Africa, Int. J. Sustain. Energy Plan. Manag. 22 (2019). http:// dx.doi.org/10.5278/ijsepm.2564 [7] C. Möller, M. Faulstich, S. Rosenherber, Urban-rural relations in renewable electric energy supply – the case of a German energy region, Int. J. Sustain. Energy Plan. Manag. 21 (2019). http://dx.doi.org/10.5278/ijsepm.2019.21.7 [8] K. Kuriyan, N. Shah, A combined spatial and technological model for the planning of district energy systems, Int. J. Sustain. Energy Plan. Manag. 21 (2019). http://dx.doi. org/10.5278/ijsepm.2019.21.8 and co-authors look into Osnabrück, Germany – and surrounding rural municipalities. Kuriyan and Shah [8] develop a combined spatial and technological tool for designing and analysing district heating systems as a part of the THERMOS project. Optimisation of district heating system design in multi- node systems turn out to be time consuming, thus optimisation of the design process is one of the targets in the authors’ work. References [1] A.G. Khaleel, M. Chakrabarti, Energy modelling as a tool for curbing energy crisis and enhancing transition to sustainable energy system in Nigeria, Int. J. Sustain. Energy Plan. Manag. 21 (2019). http://dx.doi.org/10.5278/ijsepm.2019.21.2 [2] A.A. Razmjoo, Investigating energy sustainability indicators for developing countries, Int. J. Sustain. Energy Plan. Manag. 21 (2019). http://dx.doi.org/10.5278/ijsepm.2019.21.5 [3] A.I. Ugulu, Barriers and motivations for solar photovoltaic (PV) adoption in urban Nigeria, Int. J. Sustain. Energy Plan. Manag. 21 (2019). http://dx.doi.org/10.5278/ijsepm.2019.21.3 http://dx.doi.org/10.5278/ijsepm.2019.21.4 http://dx.doi.org/10.5278/ijsepm.2019.21.4 http://dx.doi.org/10.5278/ijsepm.2019.21.8 http://dx.doi.org/10.5278/ijsepm.2019.21.8 _GoBack