FAVOURITES: 9 September 2011. [Updated] The Zero Carbon Australia Stationary Energy Plan, published recently by Beyond Zero Emissions, has received widespread support from eminent scientists, academics, industry leaders and energy sector businesses.
At the heart of the plan is a strategy to move Australia away from a dependence on fossil fuels to 100 per cent renewable energy. The report debunks the argument so often put forward by critics that renewable energy can never supply baseload energy because it is unreliable and too expensive.
Mike Sandiford, Professor of Geology and director of the Melbourne Energy Institute at the University of Melbourne, which sponsored the report, describes the Zero Carbon Plan as ” an extraordinary and pragmatic roadmap to a new and more sustainable energy system in Australia, and ultimately our region.”
In an opinion piece on ABC’s The Drum Unleashed, Pablo Brait, director of strategic planning with Beyond Zero Emissions, described the motivation behind the report:
“The Zero Carbon Australia report is the culmination of 12 months of pro bono work by engineers, scientists and postgraduate university students, performing the research that no Australian government has been prepared to undertake.
“The result is a truly innovative collaboration the likes of which has never been seen before in Australia.
“It is a true failure of leadership that our elected representatives have not developed a comprehensive transition plan for the energy sector even though it is at the heart of climate change mitigation efforts. Instead it has been left to a group of concerned citizens to pick up the slack.”
Shifting from fossil fuels to renewables
The report proposes a complete shift away from fossil fuels, combined with increased energy efficiency:
“With a combination of energy efficiency, fuel switching from gas and oil to electrified energy services, then using a combination of commercially available renewable energy technologies, Australia’s energy needs can be met with 100 per cent renewables. Wind and concentrating solar thermal or CST, with molten salt storage are the two primary technologies used, with minimal contingency backup from biomass and existing hydro. Modelling on a half-hourly timescale shows that this combination can ensure 100 per cent reliable supply…..
“The ZCA2020 plan proposes a complete phase-out of all fossil fuels (natural gas, oil and coal), starting from 2011. By 2020, total Australian energy consumption is reduced to less than half of business as usual projections. This is the result of moving to a higher efficiency, zero carbon, electricity-based energy system that applies negative pressure on energy costs in the long term.”
The Plan would be implemented over a 10 year period and would require an annual investment of $37 billion or 3 per cent of GDP. The estimated funding cost, including generation and grid upgrades, would be equivalent to an additional 6.5 cents/kWh on delivered electricity. This represents an extra $8 per week per household, says the report, the same premium paid for Green Energy.
Under the plan, it is projected that 2020 grid electricity demand will be over 40 per cent higher than today, from 228TWh/yr up to 325TWh/yr:
“This increase in electricity demand is due largely to the switch of services currently provided by gas and oil to be supplied more efficiently with renewable electricity. The increase is significantly offset by ambitious but achievable electrical energy efficiency targets. This is more electricity demand than would be required under Business-As-Usual growth.
“To meet this demand, a combination of wind and solar thermal with storage is proposed as the primary electricity generation technologies. Biomass and hydro are utilised as contingency, supplying about 2per cent of annual electricity.”
The energy demand forecast is based on:
- Business As-Usual projections of energy consumption, driven by population growth, and growth in per-capita consumption
- Energy-efficiency improvements for existing electricity use, a cost- effective strategy that reduces the need to increase installed generating capacity
- A fuel switch from gas and oil for end-use applications to renewable electricity. Electrical systems for heating and transport can have significantly higher efficiency
- Improved thermal insulation for buildings to flatten demand peaks and seasonal variations in demand, reducing the need for peak generators
- Energy supplied from onsite generation, which displaces grid electricity.
An integral part of the Zero Carbon Plan is much greater energy efficiency. It assumes an energy efficiency gain of 33 per cent per capita compared to current energy services. This is an achievable target, the report says, and will bring Australia in line with other modern economies. Germany’s per capita energy use, for example, is currently 30 per cent less than Australia’s and will be further reduced over the next 20 years due to ongoing official government programs.
The report outlines the areas where energy efficiency would be improved:
“The ZCA2020 Plan calls for energy-efficiency measures to progressively reduce electricity used for current services. Examples include efficient appliances, improved building design, retrofitting insulation, double- and triple- glazing, as well as improved industrial efficiency.
The switch of end-use applications from gas and oil to electricity is expected to yield substantial efficiency gains and result in a reduction in total energy use. Key switched services include:
- Low-temperature gas heating (such as space and hot water) is replaced with highly efficient electrical heat pump heating, bringing an average gain in energy efficiency of around 3:1
- High-temperature heating applications (such as cooking, industrial processes) can be converted to induction or electric resistance heating. This is typically more efficient, with no losses from hot flue gases caused by fuel combustion
- Replacement of oil with electricity for cars, freight rail, and passenger rail transport brings a high gain in overall efficiency. This occurs partly through the inherent efficiency of electric motors (>80per cent) relative to internal combustion engines (<20per cent) and partly through a proposed modal shift to light and heavy rail for both passenger and freight.
Renewable energy technologies
The chosen renewable energy technologies in the Plan are a mix of wind turbines, concentrating solar thermal with storage, small-scale solar, and contingency capacity from biomass and existing hydroelectricity, as outlined below:
- Wind Turbines – wind generation is a key component because of its relatively low cost and industry maturity. Wind is proposed to meet 40 per cent of the total grid-connected demand
- Concentrating Solar Thermal – large-scale Concentrating Solar Thermal with molten salt storage offers reliable electricity 24 hours per day. Solar power towers are proposed because of their technological maturity, higher operating temperatures and efficiency compared to other technologies. CST is proposed to meet 60 per cent of the total grid-connected demand.
- Small-scale solar – small-scale solar photovoltaic power has a role in reducing the demand for grid electricity during sunlight hours. This in turn allows the CST plants to accumulate more stored energy for release at night
- Hydroelectric generators – existing hydroelectric generators have a useful role in providing first-dispatch backup and peaking power
- Biomass contingency – backup from crop-residual biomass for the CST plants offers energy security, protecting against occasions when a combination of low wind and low daily solar radiation occurs.
“The plants are located at sites around Australia that are selected for their wind availability, solar incidence, ability to support economies of scale, transmission costs, and geographical diversity‚ giving 23 sites for wind, and 12 sites for CST. Extra generation capacity is also costed for remote off-grid power generation.
Contingency will be provided by existing hydropower capacity, and from biomass fired heaters attached to some of the CST plants.”
Concentrating Solar Thermal – what is it?
Sixty per cent of the power under the Zero Carbon Plan is provided by Concentrating Solar Thermal (CST) with storage, which the report says will provide reliable, 24-hour dispatchable power through molten salt thermal storage. CST is described in the report:
“There are four main types of CST systems: power tower, dish, linear fresnel and parabolic trough systems. Power towers are selected for their high temperatures and efficiency, high year-round solar collection performance, and easy integration with molten salt thermal storage.
“Solar thermal power towers with storage have been proven at commercial scale during three years of operation of the Solar Two tower in the USA, from 1996 to 1999. There are a number of companies building and operating utility-scale solar thermal with storage around the world, including Torresol, SolarReserve and ACS Cobra.
“The proposed CST power towers consists of a central tower receiver surrounded by a field of 18,000 heliostats. The heliostats are two-axis tracking mirrors that follow the sun, reflecting focused sunlight on the receiver heating it to at least 565oC. Importantly, the ability of heliostats to track both the daily passage and seasonal elevation of the sun’s position in the sky means they have increased solar energy collection efficiency compared to systems with less tracking ability.
“The receiver is similar to conventional boiler tubes, except that instead of water as the working fluid, molten salt is used. The molten salt flows through the receiver accumulating thermal energy from the focus and then flows into the hot salt tank. When there is a demand for electricity, the hot molten salt is passed through a heat exchanger to generate high-temperature steam for the turbine. The steam spins the turbine to generate the required amount of electricity. The heat extracted from the molten salt cools it to 290oC (still molten), and it is returned to the cold tank where it waits to be pumped up the tower again for heating.”
The Plan specifies a number of inland CST plants with transmission cables carrying power to densely populated coastal areas. It also factors in the impact of seasonal solar variations, which it says can be mitigated by choosing a number of geographically diverse sites for CST plant locations.
The report dismisses arguments of renewable energy not being able to provide baseload power:
“These power towers are able to operate at 70-75per cent annual capacity factor, similar to conventional fossil fuel plants. They are capable of dispatching power 24 hours a day, and are as reliable as conventional ‘baseload’ power. Furthermore, they are in fact more flexible to meeting varying demand. The steam heat-exchange and turbine systems are specifically designed for rapid start up, allowing CST to balance changing electricity demand patterns, and providing ‘firming’ power to more variable wind generation.”
There are 12 CST sites in the Plan, each with an operational capacity of just over 3,500MW. On each site there would be13 CST power towers rated at 217 MW. In total, the land use for CST sites is estimated in the report to be 2,760km2, less than 0.04per cent of Australia’s total land mass. This, says the report, is less than the land area of the largest single cattle station, or about the size of Kangaroo Island. Water use in the CST plants is minimised by using air cooling, reducing the rated plant output by 1.3per cent, but requires only 12per cent of the water used in a conventional power station.
“The total CST water consumption is projected to be 0.4per cent of Australia’s total water consumption, significantly less than the water used by existing fossil fuel plants. A preliminary study of water resource availability at each of the 12 sites has found that there is ample water available for the proposed CST usage of 6.3GL/yr per site. Even in Kalgoorlie, mining activities currently use twice this.”
The ZCA2020 Plan proposes that 40 per cent of Australia’s total estimated electricity demand be met by wind power. The plan takes into account the variable nature of wind power, and has allowed for 15 per cent of the combined rated capacity (50,000 MW) of all wind generators installed across the country to be considered ‘firm’ wind output. This ‘firm’ wind output is as reliable as conventional baseload power, the report says. It goes on to explain the role of wind power in the Plan:
“To supply 130TWh/yr from wind power, 50,000MW of wind capacity is proposed. This requires the construction of an additional 48,000MW of wind turbines on top of Australia’s 2010 wind capacity. We propose that 6,400 high quality, technologically advanced 7.5MW wind turbines be utilised. E126 Enercon turbines are specified as they are currently the only commercially available 7.5MW turbines. Large turbine sizes enables the extraction of more energy from a given site by tapping into stronger and more consistent wind resource at higher altitudes.
“The Plan proposes 23 sites for wind power, each consisting of either 2,000 or 3,000 MW of turbines. The geographically dispersed wind sites exploit the diversity in weather systems that occur simultaneously across the Australian continent and counter localised wind variability.
Attempts have been made to select wind sites according to highest average winter wind speeds rather than highest average annual speeds, to accommodate the projected winter peak.
According to the report, wind power integrates well with CST, because CST has storage that can readily dispatch power, providing back-up for wind power during lows in energy production. Similarly, periods of high wind output offset CST electricity production, and allow the CST plants to direct more heat to storage for later use.
Biomass and hydroelectric backup
To insure against the possibility of simultaneous cloud cover over several of the CST sites coinciding with a period of low wind and high demand, the Plan uses a system of biomass co-firing of the CST plants to ensure energy security. The proposed system incorporates a simple biomass- fired thermal heater alongside the molten salt tanks at the actual CST sites. Biomass is burnt, and the energy used to heat the molten salt reservoirs, so that the existing steam power cycle, turbine and transmission can be utilised.
Hydroelectric backup is also included in the Plan but is limited as outlined below:
“A combination of 5 GW of existing hydro capacity and 15 GW electrical equivalent of biomass-fired backup heaters will be sufficient to ensure reliable supply of electricity even at times of low wind and solar radiation at several power plants/sites. ZCA2020 does not propose additional hydro dams in Australia. Future work will investigate the feasibility of upgrading existing hydro dams to pumped storage hydro for long-term seasonal supply, which would replace biomass backup.
A new national grid
The zero carbon Plan also proposes a comprehensive upgrade to Australia’s electricity grid to allow full utilisation of the distributed renewable energy network. Creation of the new national grid would require four main upgrades to the existing grid at a total cost of $92 billion. These include:
1. “Plug in” connections from proposed power generators to the electricity grid
2. Interconnection of the three main existing grids
3. Transmission upgrade of existing grids to provide resilience and reinforcement.
4. More active demand-side load management
The Plan also allows for reduced energy demand because of conversion of gas heating to efficient electric heat pumps and building efficiency programs. Peak demand would be reduced through active load management using SmartGrid systems.
The feasibility of the new transmission network outlined in the Plan is backed up by a review by engineering firm Sinclair Knight Merz, which found:
“The transmission scenario proposed is technically feasible in terms of capacity and reliability. In addition, the proposed transmission uses mature technology with proven capability around the world.”
According to the modelling used in the Plan, many more jobs are created with the construction of a 100 per cent renewable energy grid than are lost with the phasing out of coal and gas. The report estimates the Zero Carbon Plan will create up to 80,000 jobs from installation of renewable energy generation at the peak of construction, and over 45,000 jobs in operations and maintenance that will continue for the life of the plant. If half the manufacturing for wind turbines and heliostats is done domestically, this would also create up to 30,000 jobs in manufacturing.
The report concludes:
“The ZCA2020 Stationary Energy Plan outlines a fully costed and detailed blueprint for transforming Australia’s energy sources to 100 per cent renewable supply. This is achievable using technology that is commercially available today, with no technical barriers to their deployment.
Implementing the proposed infrastructure in ten years is well within the capability of Australia’s existing industrial capacity. The required investment is the equivalent of a stimulus to the economy of 3 per cent of GDP. 100 per cent renewable energy in ten years is achievable and necessary, ensuring Australia’s energy security, national security and economic prosperity for the future. Australia has some of the best renewable energy resources in the world, and should be positioning itself as a leader in the emerging renewable energy economy. What is required to make this happen is leadership from policymakers and society, with firm decisions made quickly that will allow this transition to occur.”