Electricity generation is the single largest source of carbon dioxide emissions in Australia, and the success of the Solar Tower will be a direct result of the community’s desire to increasingly source its energy from renewable sources that do not generate greenhouse gas emissions.
SOLAR TOWER TECHNOLOGY
In the early 1980s, Professor Jörg Schlaich designed the Solar Tower power plant, bringing together three well-known robust principles in a unique way:
1. The use of the sun’s radiation to heat a large body of air (greenhouse
effect lets light in, direct and diffuse, but does not let heat out);
2. Hot air rises (as through a chimney); and
3. Movement of air as energy source to drive large turbines to generate
electricity (basic engine).
Sometimes called the hydro power plant of the desert, it works in much the same way, but upside-down. Where the hydro system drains a lake through a narrower opening to drive a turbine, the Solar Tower sucks warm air through the chimney-like tower to drive a turbine.
As with all ideas that appear simple, there is more to it. To be economically viable, the Solar Tower power plant has to be big – very big. The prototype that successfully generated 50kW of electricity for 15,000 hours over 7 years had a collector roof 240m in diameter and a tower 197m high. The prototype was built in Manzanares in Spain to test the concept, and is now decommissioned. The full-scale plant under evaluation by EnviroMission here in Australia needs to be 5 km across and 1 km high to achieve 200 MW of electricity generating capacity. This capacity can power 200,000 homes, equivalent to a city such as Hobart. The plant will cover an area of at least 20 square kilometres, and it will be Australia’s, and the world’s, tallest and largest engineered structure.
Jörg Schlaich is a senior partner with Schlaich Bergermann Partners (SBP), leading consulting engineers from Stuttgart, Germany. The firm is the world leader in lightweight construction of towers, roofs, bridges and “suspended” buildings, including the Munich Olympic Stadia and the Ting Kau Bridge in Hong Kong. SBP is the original developer of the Solar Tower renewable energy, devoting excess of 25 years of research and development to the concept. In parallel with SBP’s input, over A$75M has been invested to bring the technology to commercialisation.
The Collector System
The 5 km diameter collector system will have a slightly rising roof of semi-transparent glazed material, standing between two and twenty metres above the ground on steel supports at 6 m intervals. The 4 mm glass (or plastic) will be held by steel horizontal prop girders and transverse steel plates. The girders can carry rails for access to the glass sheets. For example, if there is heavy dust, vacuum cleaners can travel along the rails to clean the glass. Plastic may be cheaper, but tends to become brittle from UV radiation. Under the collector roof, air temperature is about 30°C - quite habitable – and wind speed will be about 32 kmph – equally benign.
The Tower
The tower is not as complicated as other tall structures because of its simple task. It will be constructed (slip form) from reinforced concrete, 1m thick at the base, tapering to 25 cm thick at the top. An equally strong tower could comprise concrete and steel. The diameter of the tower at the base will be comparable to that of a football field. The Solar Tower uses a unique technique to counter the ovalisation that affects many tall cylindrical structures. At six intervals inside the tower - 280m, 460m, 600m, 730m, 860m, 990m - a series of internal metal horizontal supports (similar to that of bicycle wheel spokes) are constructed to create added strength and also serve to assist as platforms. The airflow loss from the spokes is no more than 2%. Air speed is constant through the tower, with some updraft at the top.
The Turbines
The original design proposed one large (90m diameter, 200 MW) turbine with 12 blades made of light alloy metal, with the propeller set horizontally at the base of the tower. The single turbine is most efficient, but would have to be purpose-built. As there is some uncertainty over the development of shrouded wind turbines to the required scale, and as there are existing manufacturers for smaller scale turbines, the first plant will use 32 small (6.5 MW) turbines set vertically in the transition area, where the collector system meets the tower.
Night and Day
The Solar Tower’s supply curve is approximately bell shaped, peaking
with that of the sun’s intensity. During summer, it is similar to
the demand for air-conditioning, and the hotter the day, the more efficient
the power plant. If a more even supply of electricity is required,
energy can be stored under the collector during the day using black plastic
tubing filled with water. Water has a heat storage capacity about
6 times that of soil. Further enhancements such as doors that slow/stop
the turbines can be installed. Total “fire-up” time is 24 hours,
however turbines can be independently slowed/shut down in groups of 4.
This flexibility allows output to be adjusted for shifting demand patterns.
Storage could reduce the peak capacity from 200 MW to a constant 80 MW,
although the intention is to operate as a peaking station. Annual
production from the proposed power plant is just over 700 GWh.
Optimisation
Power output is determined by the height of the tower, the size of the collector roof and the extent to which it is glazed (single or double). The relationships are roughly proportional, i.e. doubling the height of the tower or doubling the width of the roof doubles output. The optimization process (currently underway) therefore takes into account the relative cost of glass/plastics, glazing, cement and transport.
Construction
EnviroMission is confident that the design concepts and construction methods are feasible for the proposed scale. However, the scale of construction is comparable to the Loy Yang Power Station, and issues relating to supply of materials are now being addressed. The main questions to answer are:
1. Can Australia, and the locations viable on other criteria, economically
supply the necessary quantities of materials – 20 km2 of glass and/or plastic
and 400,000 cubic metres of concrete? (Loy Yang required 450,000
cubic metres of concrete.)
2. Can glazing material with suitable optical and heat containment
properties be produced?
3. Is it best to build the tower in sections, then pump the concrete
to the top of each section to construct the next section, or is pre-fabrication
more appropriate?
Technical feasibility is confirmed in assessments by engineering firm Sinclair Knight Merz and world expert in tall structures, Emeritus Professor Bill Melbourne, from the Department of Mechanical Engineering at Monash University. The challenge for EnviroMission is to establish the financial feasibility, and attract long-term investor support.
SOLAR TOWER ECONOMICS
Revenues
EnviroMission’s Solar Tower power plant will compete directly with all other generators in the national electricity market, either as a market generator selling into the electricity pool, or as a non-market generator selling its output locally; and it will compete with other renewable sources of power. The price will have two components – the wholesale market price for electricity and the wholesale market price for renewable energy certificates.
EnviroMission estimates total unit revenue for renewable energy in the Victorian pool at A$92 per MWh by 2005 (A$45 pool price, A$47 renewable energy certificate price). Revenues for Solar Tower electricity are expected to be enhanced by A$18 in premium for locational benefits, and A$5-15 in premium for peak sales.
The Electricity Market
The electricity market appears to have stabilized over 2001, with average prices around $A25-30 per MWh, although higher prices and variability are expected for the peak months from December to February. Long-term forecasting by NEMMCO indicates continuing summer shortfall in Victoria and South Australia, and adequate capacity in New South Wales and Queensland.
Source: NEMMCO
The annual average price for the same period varied across the southern regions:
NSW A$35
Vic A$38
SA A$46
Snowy A$34
The Market in Renewable Energy Certificates
Renewable energy certificates (RECs) are a new form of currency. Power generators create the certificates (print money!) by producing and despatching eligible electricity, i.e. from renewable sources developed (new or incremental) since 1997. Under the legislation, renewable energy sources are:
hydro; wind; solar; bagasse; black liquor; wood waste; energy crops; crop waste; food and agricultural wet waste; landfill gas; municipal solid waste combustion; sewage gas; geothermal-aquifer; wave; ocean; tidal; and hot dry rocks.
To qualify for certificates, generators must be accredited with the Office of the Renewable Energy Regulator (ORER), and the Solar Tower plant would qualify.
The demand for RECs is created by the Australian Government’s Mandatory Renewable Energy Target (MRET) legislation. The target requires the generation of an additional 9,500 GWh pa from renewable sources. Annual targets are:
2001 300
2002 1,100
2003 1,800
2004 2,600
2005 3,400
2006 4,500
2007 5,600
2008 6,800
2009 8,100
2010 9,500
Each wholesale electricity purchase will generate a liability for the purchaser to obtain and then surrender RECs as a percentage of total MWh bought. In 2001, this percentage was 0.24% of amount purchased. Under the regulation, the percentage is set to achieve the targeted GWh.
However, the original intention was to lift the total percentage that renewable sources contribute to generation from 10.5% in 1997 to 12.5% by 2010. The increment of 9,500 assumes total generation in 2010 will be 204,000 GWh, or an increase of less than 10% over 10 years. Should the Government pursue its original intention, the required increment in “green” power could range from 9,500 to 13,000 GWh, as calculated by Australian EcoGeneration Association (AEA) based on forecasts by the Electricity Supply Association of Australia (ESAA).
Purchasers meet their obligation by acquiring and surrendering RECs. If a purchaser owns more RECs than required in any year, it can carry forward a surplus to the following year, or sell RECs to other parties. Failure to surrender the required number of RECs results in a penalty A$40 each (i.e. per MWh). The penalty is not tax deductible.
The base price for RECs would appear to be the penalty. The price purchasers will be prepared to pay above $A40 will depend on their tax position. Fierce price competition between renewable energy suppliers seems unlikely given the relatively high cost of generation and the low likelihood of significant excess supply of RECs.
From 1997 until implementation of the new legislation, 720 MW of additional “green” capacity has been installed. In December 2000, AEA identified over 1,000 MW of capacity from 77 committed or proposed projects with the new regulation. Depending on the conversion factor, this translates into GWh in the range 6,700 to 10,000 GWh pa (based on conversion factor 0.4 to 0.6).
“Even if other renewable sources can meet the lower target, they cannot meet the higher target.” Roger Davey, CEO, EnviroMission Limited
In contrast to the large number of mostly small-scale renewable power projects in development, one Solar Tower power plant will meet 7.5% of the target on its own. The largest planned wind energy farm will be at Woolnorth on the north-west coast of Tasmania with a capacity of 130 MW from 80 turbines. The Tasmania west coast could eventually supply 1,000 MW, dependent on the Basslink development. Hydro Tasmania chairman, Peter Rae estimates that Tasmania could provide close to 30% of Australia’s renewable energy target. Compared to wind energy, the Solar Tower creates less visual impact by being inland, rather than on scenic coasts. However,
“Every renewable energy generator is important to the environment and
the mandatory energy target, as a gap exists in large-scale consistent
renewable energy generation.” EnviroMission Fact Sheet 6.
Costs
EnviroMission’s preliminary estimate of total capital cost is A$600-700m, including $270m for the collector and $230m for the tower. It expects contractors to be conservative for the first tower, and over-engineer to some extent, adding to the initial cost. The optimisation process includes an investigation of the best mix of construction materials to minimise the capital cost.
Running costs are relatively low, so overall cost in A$ per MWh is sensitive to the interest rate - cheap solar power needs cheap money. The estimated unit cost is commercially sensitive information, however EnviroMission expects a level comparable to that of other renewable energy technologies.
MANAGEMENT
The Solar Tower technology binds EnviroMission, Energen Global Inc (not to be confused with the listed US oil and gas company, Energen Corporation), and SBP together through ownership and commitments. The link between EnviroMission and SBP was formalized with the agreement to provide tender design services to June 2002 in exchange for A$800,000 in the form of 1 million ordinary shares issued at 80 cents each (share price was 25c as at end 2001), and detailed design services over the life of the project for 10 million shares under the same terms (A$8m equivalent).
The links with Energen are reinforced through Board representation. Former EnviroMission CEO, Stephen Graves (past Treasurer of Mobil Oil Australia P/L) has returned to the United States to take up the executive position of Chief Operating Officer with Energen Global Inc. He remains a non-executive director on EnviroMission’s board.
Executive Director and new CEO, Roger Davey, has extensive experience in commodity and financial risk management. He continues in his role as President and Executive Director of Energen Global Inc. in the United States.
Enviromission’s board is chaired by Deputy President of the Australian Institute of Energy, Martin Thomas. As former principal of Sinclair Knight Merz, Martin has over 30 years’ experience as consulting engineer in the power and energy sector, and has played a leading role in the development of renewable energy in Australia. Non-executive Director, Geoffrey Parkinson, has 27 years’ experience in banking and finance.
The management team comprises: David Penkethman - GM Engineering; Des Haberman - GM Government Relations; John Shrives - GM Retail; Richard Parker - GM Business Development; and Jacky Walker – CFO and Company Secretary. All have extensive energy industry experience.
Reflecting the scale and challenge of the project, EnviroMission established an advisory board to provide guidance in areas such as renewable energy generation, energy industry issues and needs, science and research & development, civil engineering and construction, large-scale manufacturing, environmental and ecological issues, and regional infrastructure and economic development. The board includes familiar eminent Australians - Martin Thomas AM, The Hon. Peter Rae AO, Dr. John Nutt AM, Professor Ian Lowe AO, and Richard Farley.
LOCATION, LOCATION, LOCATION
The preferred site is Ned’s Corner Station near Mildura. EnviroMission
has an option over the property, which is 70 km west of Mildura.
Keeping with the “big” theme, the station is the largest parcel of privately
titled land in Victoria, being some 30 km long and 15 km wide. The
land, comprising mainly flat saltbush, includes water access rights from
the Murray River of 110 Mlpa. The A$2.6m option expires on 31 March
2002, and the decision to buy will depend on the results of extensive testing,
including soil and sub-soil analysis to evaluate suitability for the foundation
structure of the power plant’s tower, as well as site specific solar measurements,
and construction material sample testing and evaluation. The current
round of geotechnical testing will confirm or refute the site’s suitability.
| SITE SELECTION CRITERIA NED’S CORNER | |
| Solar radiation at minimum 2,000 MWh per square metre per year | yes |
| Low humidity | yes |
| Access to power grid above 220 kV | South Australia/Redcliffs main line. |
| Proximity to local electricity market | Mildura/Murray Basin |
| Flat open land | yes |
| Soil/substrata stability ? | To be tested before purchase. |
| Road/rail access | yes |
| Land use restrictions – native title, environmental, building/height restrictions ? | Environmental issues to be identified and addressed through the Environmental Impact Statement |
| Flight path restrictions ? | To be investigated. |
| Access to concrete, aggregate and sand | yes |
| Local and State Government support | yes |
| Tourism potential | Mildura’s image as a sun/solar city*. |
| Agricultural opportunities ? | To be investigated. |
| Telecommunication/defence opportunities | yes |
| Salinity reduction ? | To be investigated. |
The main criteria are solar radiation (main input), flat open land (cheap to buy and build on) access to the grid (cheap to connect), and low humidity (high humidity creates solar rain). Mildura is currently in the front running, and a further 5 sites have been identified as potential locations – the Kalgoorlie region in Western Australia, the Olympic Dam region in South Australia and 3 sites in Queensland (where the higher humidity is balanced by higher solar radiation levels).
THE BIGGER PICTURE
The Solar Tower produces zero emissions and abates over 900,000 tonnes of greenhouse gases when compared to coal-fired energy generation. According to EnviroMission, life-cycle analysis (energy use and greenhouse gas emissions) indicates the payback period is about 2½ years (i.e. in 30 months, it saves an amount of carbon dioxide emissions equivalent to the emissions produced when the glass, cement, steel, and turbines are produced using non-renewable energy). The analysis assumed the use of glass for the roof, and the use of other materials could affect the pay-back period in either direction.
The Solar Tower power plant has been proved technically feasible for many years. It was not developed sooner due to the relatively higher cost compared to fossil fuel generation. These cost differences did not take into account the impact on the community of greenhouse gas emissions. These environmental costs are now implicitly accounted for through the renewable energy certificate penalty. The trend is towards greater use of renewables, and this trend is supported across the energy industry. The AEA recommends increasing the MRET to 5% from renewable sources by 2010, which would add nearly 12,000 GWh to the 2010 target. Further, the penalty for non-compliance is likely to increased at least with inflation. With retail contestability consumers have the opportunity to satisfy their preference for electricity from renewable sources. Implementation of the policies of the Australian Labor Party and the Australian Democrats would include stronger targets as well as national reporting of fuel source and emissions at the retail level.
Government support for the Solar Tower project is expected with facilitation through the planning approvals process by the Victorian Department of State and Regional Development. EnviroMission is also seeking major project facilitation (MPF) status for assistance and associated tax benefits through the Federal Ausindustry and Invest Australia, joint funding for development to investigate suitable materials and other design parameters. Renewable energy generators can also seek assistance through the Federal Government’s greenhouse gas reduction programs, with funds totalling A$1bn available, including A$400m to support the development and uptake of renewable energy technology. While assistance with development will be sought the project will not rely on government funding, and will be competitive in the private investment market.
Australia is ideal for the first full-scale plant because of its solar radiation levels; geological stability; low land costs; proliferation of suitable terrains located close to electricity grids; leading construction and operating standards; an environmentally aware community; and legislated government support and incentives for renewable energy generation. Taking a broader view, the technology is under consideration for cleaning the air in Los Angeles. Australia may even have the opportunity to demonstrate a technology that could bring the third world closer to the first. The inventor, Jörg Schlaich, can envisage a day when the abundant solar resource of the world’s deserts will supply the power for ecologically sustainable development in the majority world.
TIMETABLE AND CONTACTS
Until March 2002 EnviroMission will be busy with a design review, site selection, technical optmisation, electricity market analysis, and financial evaluation.
By December 2002 Complete tender design and arrange equity and project debt funding. Most likely structure is a joint venture with suitable construction and manufacturing partners.
End 2002 Let contracts.
Early 2003 Commence construction.
Late 2005 Complete construction, and commence electricity generation.
2010 Complete 4 more Solar Tower power plants.
If you wish to find out more about the Solar Tower and EnviroMission,
the website is www.enviromission.com.au, and SBP’s website is www.sbp.de.
The EnviroMission office is located at:
Suite 1, Level 1
1121 High Street
Armadale, Victoria 3143
Australia
PO Box 125A
Armadale, Victoria 3143
Australia
Phone: +61 3 8823 5355
Fax: +61 3 9822 8186
Email: evm.admin@enviromission.com.au
Note: The author holds shares in EnviroMission Limited.
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