Thursday, July 11, 2013

Suburban energy collectors could power EVs

SOLAR POWER: Photovoltaic panels for car charging on the Wellsford Library north of Auckland.
The sprawling suburbs of Auckland, reviled by many planners and politicians, could be a key producer of the power needed for a future fleet of electric vehicles.
An Auckland University study found low dense suburbia would be the most efficient collector of solar energy in the city. It could generate enough excess electricity to power the transport needs of the residents of suburbia, and contribute to peak daytime electrical loads in the city centre.
The study, published in Energy Policy, does acknowledge that for the suburbs to power an electric vehicle fleet, the vehicles would have to be at home in the middle of the day.
While that went against current commuting habits, the increased value of charging from home during the daytime could encourage the use of public transport for commuting, the study said.
It pointed to research that found 78 per cent of a driver's mean travel distance in major urban areas was for reasons other than going to work. Those uses often happened outside peak photovoltaic generating times.
"Through the implementation of smart technologies, suburbia could transform to an energy contributor, not only for its own transport needs but for the city as a whole," the study said.
Electric vehicles could store electricity to feed into the grid to reduce peak demand, or feed into houses to offset or replace grid supply.
"If this is to be effective, controls of new suburban development may be needed that require the installation of (photovoltaics) on roofs along with smart meters and appropriate charging facilities for vehicles."
The study took a sample of the main building types in Auckland and reassembled them into a representative cross-section to work out the maximum potential energy that could be made available by efficiently installing photovoltaic systems on buildings throughout a city.
Several characteristics made Auckland an interesting case study, it said.
Annual solar radiation in Auckland was similar to that in Barcelona, and well above those in Freiburg, Germany where photovoltaics had been extensively installed. Auckland had grown around car use, so was dispersed and dependent on imported oil.
Energy consumption of different types of buildings was compared to the potential amount of electricity that could be generated by photovoltaics.
Only detached dwellings had a photovoltaic generation potential greater than total energy use. That was only the case if solar hot water heating had been installed, reducing total household energy consumption by about 20 per cent.
It was assumed 4sq m of efficient roof area per household would be dedicated to hot water panels, which were more efficient and cost effective than photovoltaics.
Results implied detached dwellings could contribute surplus energy to the city during the daytime, the study said. But while feeding electricity generated by photovoltaics into the grid may be appropriate in countries where there was a subsidised feed in tariff, that was not the case in New Zealand.
Alternatives were to satisfy household demand first before feeding the surplus into the grid, or store the surplus in batteries - either fixed or in electric vehicles - which could then be be used for travel or feeding into the grid at the optimum time.
Other research important to the study's conclusions forecast a fall in price of electricity generated by photovoltaics and a rise in the price of grid-based electricity, until the photovoltaic electricity became cheaper. That was expected to happen in the early-2020s, about the same time as the number of electric vehicles were forecast to start rising sharply.
"With (photovoltaics) as a means of generating electricity cheaper than the grid and no incentive to feed it into the grid, the logical choice is to use the electricity for both household use and for transport," the study said.
The future of transport in Auckland, and many other cities, would be linked to the emerging technologies of photovoltaics, electric vehicles, smart meters, and the synergies between them.
A compact city may be more efficient in cities where most transport was in vehicles with internal combustion engines, the study said. But a dispersed city would be more efficient when electric vehicles were the main means of transport and photovoltaics the main energy source.
The options and choices of fully or partially charging an electric vehicle by photovoltaics or by the grid at different times of the day or night needed to be studied once electric vehicles started to have market penetration.
- © Fairfax NZ News