By Upasana Bhattacharjee
Recent research by the Australian National University (ANU) has shown that electricity grids with 100 per cent renewable energy are viable when using pumped hydro storage.Wind and solar photovoltaics (conversion of light to electricity) technology alongside pumped hydro storage can sustain the zero-emission grid. This technology is set to eliminate Australias dependence on coal and gas-fired power, according to lead researcher Professor Andrew Blakers.
ANU has worked out a model that is set to provide 100 percent renewable energy to Australia. While the technology and existing infrastructure still need augmentation, the next two decades could see substantial progress.
The STORES Technology
ANU is mapping the potential of Short-term Off-river Pumped Hydro Energy Storage (STORES) technology.STORES sites are pairs of reservoirs on hilly terrain (typically 10 hectares each) that are separated by an altitude difference of 300 to 900 metres. These reservoirs are joined by a pipe with a pump and turbine. Water is circulated between the upper and lower reservoirs in a closed loop to store and generate power. During the day, the abundance of electricity along with solar and wind energy pumps water upward from the lower reservoir to the upper reservoir. Water runs down through the turbine at night or when electricity is expensive. This process could increase the share of renewable energy in the grid.
Hydro power does not require a river and as such there are a large number of potential STORES sites along North Queensland, Tasmania and South Australia. Such sites require a smaller quantity of water than power generated using fossil fuels. These sites can go from zero to full power within minutes thus stabilising the grid. Further, since water is recycled between small reservoirs, the environmental impact is negligible.
Cost of the STORES
The cost of a 100 percent stabilised renewable electricity system is estimated at AU$ 75/MWh, cheaper than coal and gas powered plants. A cost model for STORES is being developed by ANU in collaboration with ElectraNet and VTara Energy Group. This collaboration will conduct a study on the Atlas of Pumped Hydro Energy Storage with an AU$449,000 financial support from the Australian Renewable Energy Agency (ARENA).
Challenges Ahead
Promising as it is, there are challenges that need to be overcome before renewable energy becomes a reality. Meeting peak energy demands in the evening when wind generation is low will require a mix of different solar, wind and storage technologies. Further, since renewable energy sources depend on natural forces, they become significantly variable. Thus, when high demand coincides with periods of low generation (like heatwaves), the supply and demand will be severely mismatched. While nuclear power is an alternative in such a scenario, there are issues of radioactive waste disposal, prevention of hazards and cost effectiveness. Additionally, a significant portion of the existing infrastructure is dependent on fossil fuel based energy. These need to be altered in order to supplement the growth and popularity of renewable resources of energy.
Relevance for today and tomorrow
This technology has been developed at a time when it is estimated that most of Australias existing coal and gas powered plants will retire within the next fifteen years. Implementation of STORES models, therefore paves the way for renewable energy for the future. They are estimated to be cheaper replacements than the existing plants that are nearing their obsolescence. Globally, solar and wind photovoltaics have been generating almost half of the new energy capacity. The statistics are only stronger for Australia. Renewable sources provide nearly all of Australias new generation capacities. Given the growing popularity of renewable sources, switching to affordable and reliable clean power in the near future seems a realistic goal.
Renewable energy is an essential component of the future. Fossil fuels are nearing exhaustion and theres a growing consciousness to curb pollution generated from such energy. In this scenario, research, development and investment in techniques to advance renewable resource generated energy assumes paramount importance. To this end, pumped hydro storage providing a country with 100 per cent clean and renewable energy serves as a major affirmation of optimism. The world is set to follow suit.