DC Grid for High Density Electric Vehicle Charging and other DC Loads, London Hydro

London Hydro, a wholly-owned subsidiary of the City of London will assess the technical and economic feasibility of creating a DC grid for electric vehicle charging and other DC loads by constructing a 2.5 to 3 MW photovoltaic solar farm on a brownfield site. The site will be located within London's east end and will act as a DC energy generation source for a new development named West 5, soon to be the largest net zero energy community in the world. The study complements the City of London's Plan and Community Energy Action Plan in addition to the London Transportation Plan for 2030, which encourages all new development or redevelopment to be electric vehicle (EV) ready. A recent study shows that EVs charged with solar energy can reduce GHG emissions, compared to a typical gasoline powered vehicle, by as much as 90 per cent. West 5 will pursue high penetration of EVs, and is exploring a marketing program of including EVs with the sale of each new condominium unit. With a target of 500 EVs out of 2,000 new homes, charging infrastructure based on renewable energy is a technical challenge and is the primary subject of this study. London Hydro will evaluate how to improve the efficiency of using solar energy to charge EV and for other DC loads in London. Photovoltaic (PV) systems produce DC electricity, and technology is used to convert it to AC for transmission over the grid. The conventional method to charge EVs using PV systems involves two steps: inverting DC power from the PV system to AC power for delivery across the grid, and then inverting AC power back to DC power to charge the DC battery in the vehicle. Each conversion step can have an energy loss of 5 to 15 per cent. Using a DC grid eliminates both conversion steps and their losses, increasing the delivery of the energy from the PV Solar Farm by 10-30 per cent for use by the vehicles. Annual direct GHG abatement based on replacing 500 gasoline vehicles with EVs will be close to 2,500 metric tonnes of CO2. The feasibility study will assess the following: • The suitability of soil conditions, site topology and location of the potential brownfield sites. • Impacts of distance from solar farm to EV chargers, and considerations for optimizing performance and system cost. • The measurement of life-cycle environmental benefits via emissions offsets achieved through use of PV for charging, and through EVs supported (track the number of vehicles that use charging facilities, and track local vehicle sales). • The creation of a medium voltage DC (MVDC) distribution link from the solar farm through downtown London to West 5. The study will need to determine the necessary parameters like line voltage and capacity, as well as identify sources for voltage converters and circuit protection. • Options for charging and billing software along the MVDC distribution link and within the West 5 micro-grid. • The DC micro-grid in the West 5 community will be tied to London Hydro’s AC feeders. As battery storage will be used with the brownfield array to smooth PV output, providing 24 hour electrical supply and minimizing the required line capacity, the study will need to design the micro-grid for proper protection of the circuit and for islanding from the AC grid in the event of a power outage. • Capturing all of the hardware costs and performing a subsequent risk analysis of the design to determine its viability. (Project description from original funding application)