Are DC Microgrids the future of power networks?

Today’s blog comes from Juilecio dos Santos Laranjeira a PhD Student in the Department of Electrical and Electronic Engineering. He is working on the systems which we use to transmit electricity around the UK. He is well placed to discuss the future of power networks.

A power inverter in the Maurice Hancock Smart Energy Laboratory

It has been a long time since alternating current (AC) won the battle against direct current (DC) in how we power our homes due to its system capacity to change voltage from a lower to higher level, allowing power to be effectively conveyed between long distances, and minimising transmission losses. However, research in DC technologies has been growing in recent years.

One key reason for this is that the interest in DC technologies, for example, mobile phones, computers, electrical vehicles, etc, and electricity generation from renewable sources, such as photovoltaics (PVs), has been growing steadily.

Currently, we transmit electricity as AC. In order to get solar energy to our homes we usually connect our solar panels to the AC operated distribution network. This requires costly inverters resulting in some loss of the power originally generated. When we plug our phones in to charge, it converts the AC current back into DC. Maybe we could save some of these losses and equipment costs if DC technologies like computers or mobile phones were directly powered by DC networks. What approach should we take to the resolution of this issue?

This is where my research comes in. I am working on what we call islanded mode (isolated) DC microgrids.  Islanded mode microgrid is a small scale autonomous local network that is charachterised by local energy generation, storage units and loads.

My project aims to understand the potential for DC microgrids. How do they cope under increased energy demand? Could the local community survive by just using a microgrid? There is also the question of connecting together DC microgrids to manage the loads of different communities. What sort of benefit would the interconnection bring, and how much?

Microgrids can have multiple uses. They could be used in urban buildings, remote villages or rural areas. I have opted for a for rural area case study in the sub-Saharan African tropical country of São Tomé and Príncipe – the second smallest country in Africa.

Electrification in developing countries is, in general, an issue of great concern due to the very poor power infrastructures that result from the lack of stability in the various sectors of the countries’ politics, economics and education. Homes in rural areas or remote villages are usually found to be the least electrified as the national grid is very limited and distribution companies are only willing to consider extensions of power lines when customers can afford to pay for the energy usage at a reasonably profitable rate. Unless a local and affordable power generation and distribution system is created, it is very likely that many people will still continue to be deprived from electricity for a very long time to come.

Beach scenery in São Tomé and Príncipe by Joao Maximo
Beach scenery in São Tomé and Príncipe by Joao Maximo

The research and development of Islanded Mode DC Microgrids employing PV Power Systems wouldn’t only be beneficial to areas poorly served by the existing AC grids, but also to homes, commercial buildings and data centres characterised by DC appliances.

Juilecio dos Santos Laranjeira

Juilecio Dos Santos LaranjeiraJuilecio is a PhD student working with Dr Adrià Junyent-Ferré and Professor Tim Green in the Department of Electrical and Electronic Engineering at Imperial College London. He is part of the EPSRC Centre for Doctoral Training in Future Power Networks and Smart Grids a collaboration between the College and the University of Strathclyde.

He joined Imperial after spending a year in Glasgow as part of the CDT programme. Before this he earned his undergraduate degree in Physics from Queen Mary, University of London and an MSc in Renewable Energy from Newcastle University.


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