Energy and Sustainability

Energy is key factor of our lives, although sometimes we forget it. We need it to achieve some of our primary needs such as preserving and storaging food, heating our houses, moving from one place to other, etc…  The way we live cannot be understood without the energy.

While the fossil fuels have been driving force of our development, the electric energy is taking more importance due to its easy way of supplying and due to the great diversity of sources to produce it. One of the advantages is that the main renewables sources (hydro, solar and wind) can be easily converted into electricity without penalizing the environment and reducing the CO2 emissions.

Some of future challenges about energy in the cities are:

  • Energy efficiency and efficient use of the energy. Each citizen can do a lot in terms of saving energy only with a rational use of it. At the same time, the technology is helping us with smart systems that optimize the use of the energy depending on the conditions. A good example is smart lightning of cities and highways. The efficiency of the power conversion is becoming very high due to some mature power electronics technology together with better semiconductor devices.
  • Including a high volume of electric vehicles. The penetration of electrical vehicles is small today Due to its relative high cost and low autonomy. However, in urban areas, it seems necessary to give steps in this direction since it is mandatory to avoid acoustic and air pollution. It is also a strategic decision in countries that import petrol since it reduces its dependence.
  • Use of DC grid distribution in buildings. The future is dc, at least for small grids where a lot of electronic equipment is connected to it. Home appliances, computers, lights…all of them work with dc and therefore the ac/dc stage can be removed. Less power consumption, less weight, less cost. Voltages such as 48 or 380V will allow this improvement.
  • Integration of renewable sources. It is not easy to include renewable sources in a city. Solar is probably the best choice although the size is limited. The PV solar panels generate the electricity in dc and it is better not to convert it to ac if it is going to be used inside the buidings. In the case of windmills, the tendency is to use a double power conversion ac-dc-ac and, of course, one can be saved in the case of dumping the energy to a dc bus.
  • Energy storage. The previous ideas (DC grid and integration of renewables) can be much more benefited if storage is included in the system. With it, it is possible to take advantage of periods with high-energy production or low-energy consumption to smooth the current demanded form the ac grid. One option is to use the electrical vehicles that are connected to grid (V2G vehicle to grid) or include specific batteries in the houses.
  • Wireless power transmission. The number of portable devices has grown at incredible speed in the last years. The main limitation of these devices is that they should be connected to the power supply very often are they should include batteries. An old technique that nowadays is being improved a lot is wireless power transmission. In some environments it makes a lot of sense to supply sensors or devices without cables but also it could make sense for electrical vehicles.


To read more:

– E. F. Schubert, J. K. Kim, “Solid-State Light Sources Getting Smart”, Science 27 May 2005, Vol. 308 no. 5726 pp. 1274-1278

– Energy Star,

– Red Eléctrica de España,

– J. Lai, “Power Conditioning Power Topologies: Power Conversion from Low-Voltage dc to High-Voltage ac for Single-Phase Grid- Tie Application”, IEEE Industrial Electronics Magazine June 2009

– J.M. Carrasco, L.G. Franquelo, J. T. Bialasiewicz, E. Galván, R.C. Portillo, M.Á. Martín, J.I. León, N. Moreno, “Power-Electronic Systems for the Grid Integration of Renewable Energy Sources: A Survey”, IEEE Transactions on Industrial Electronics, Vol.53,No.4, Aug2006

– J.S. Park, J.H. Choi, B.G. Gu, I.S. Jung, “Feasibility study of DC electrical distribution system”, 8th international conference on Power Electronics ECCE Asia 2003, pags. 2935-2938

– E. Waffenschmidt, U. Boeke, “Low Voltage DC grids“, ECPE Workshop March 13th, 2013

– K. Techakittiroj, V. Wongpaibool, “Coexistance between AC-distribution and DC-distribution: in the view of appliances”, 2nd International Conference on Computer and Electrical Engineering 421-425.

D. Boroyevich, I. Cvetkovic, D. Dong, R. Burgos, F. Wang, F.C. Lee, “Future Electronic Power Distribution System A contemplative view-”, 12th International Conference on Optimization of Electrical and Electronica Equipment OPTIM 2010, pags 1369-1380.

How the smart grid enables utilities to integrate electric vehicles” white paper, Silversprings Networks.

X. Zhou, S. Lukic, S. Bhattachary, A. Huang, “Design and Control of Grid-connected Cpnverter in Bidirectional battery charger for Plug-in Hybrid Eletric Vehicle Application”, IEEE Vehicle Power and Propulsion Conference VPPC 2009

D. Dondi, A. Bertacchini, D. Brunelli, L. Larcher, L. Benini, “Modeling and Optimization of a Solar Energy Harvester System for Self-Powered Wireless Sensor Networks”, IEEE Transactions On Industrial Electronics,Vol.55,No.7,July 2008

Wireless Power Consortium:

Kurs, André; Karalis, Aristeidis; Moffat, Robert; Joannopoulos, J. D.; Fisher, Peter; Soljačić, Marin (2007). “Wireless power transfer via strongly coupled magnetic resonances“, Science 317 (5834): 83–86.

T. Paing, J. Morroni, A. Dolgov, J. Shin, J. Brannan, R. Zane, Z. Popovic, “Wirelessly-Powered Wireless Sensor Platform”, Proceedings of the 10th European Conference on Wireless Technology

Sallan, J.; Villa, J.L.; Llombart, A.; Sanz, J.F.; “Optimal Design of ICPT Systems Applied to Electric Vehicle Battery Charge”; Industrial Electronics, IEEE Transactions on; Volume: 56; 2009; Page(s): 2140 – 2149

Chwei-Sen Wang; Stielau, O.H.; Covic, G.A.; “Design Considerations for a Contactless Electric Vehicle Battery Charger”; Industrial Electronics, IEEE Transactions on; Volume: 52 Issue: 5; 2005, Page(s): 1308 – 1314

Yasuda, T.; Norigoe, I.; Abe, S.; and Kaneko, Y.; “Contactless Charging System”; Telecommunications Energy Conference (INTELEC), 2011 IEEE 33rd International; 2011, Page(s): 1 – 7