State power utility Eskom is often criticised for its seeming unwillingness to embrace alternative and renewable energy platforms in seeking ways to align its production with fast-increasing demand. There is also some concern that its plans to reduce its carbon footprint are heavily geared towards nuclear, with the utility expecting to add some 20 000 MW of atomic energy capacity by 2025.
This criticism is unlikely to subside, particularly given that the first new base-load options selected are two 4 800-MW coal-fired power stations to be built in Limpopo and Mpumalanga provinces between now and 2015.
But Eskom insists that it is taking renewable energy into account as it proceeds, stressing that its planning has to strike a balance between the operating costs of such technology, as well as its ability to operate on demand. This said, the green shoots of what could, eventually, be developed into a fairly material renewable- energy campaign is beginning to show through, albeit modestly.
Initially, it appears the large-scale wind energy is receiving most of the attention.
In fact, Eskom has approved plans for a 100-MW wind power plant, construction of which could start in 2009, with operations possibly starting by the beginning of 2010. The development, to take place in the Western Cape province, is proposed to comprise a cluster of up to 100 wind turbines to be constructed over an area of 25 km2.
A broader site of about 37 km2, which is about 2 km from the coastline, is proposed for further interrogation, with an environmental-impact assessment (EIA) process said to be under way.
The wind project forms part of Eskom’s R300-billion capacity expansion programme to beef up power supply over the next five years.
As a precursor to initiating the EIA process, Eskom embarked on a wind resource research monitoring programme, as well as a site identi- fication and selection process to determine areas suitable for wind-energy development in South Africa.
The final scoping report notes that meteorological conditions are critically important when considering the location of wind turbines, and identifying wind-farm sites. “Ultimately, the success of the facility is dependent on the available wind resource of a particular site, such as the wind speed, turbulence, spatial and temporal variations in the wind climate, and how the wind resource is affected by the terrain.”
MAPPING THE WIND
The South African Wind Resource Database, compiled by the Department of Minerals and Energy (DME), the Council for Scientific and Industrial Research, and Eskom, identifies the West Coast north of the Olifants river as having the highest wind speeds in South Africa. They then homed in on the area for further investigation, by establishing meteorological monitoring stations to determine the potential for a wind-energy facility.
It was found that the area did indeed support all the main technical requirements for a wind-energy facility, from land availability and accessibility to proximity to the electricity grid, a crucial requirement for meeting transmission integration requirements.
In fact, an overarching objective for the wind-energy facility planning process was precisely to increase electricity production through exposure to the wind resource, while decreasing infrastructure, operational and maintenance costs as well as social and environmental impacts.
The report states that as local-level environmental and planning issues were not assessed in sufficient detail during the regional-level site identification process, these issues must be considered within site-specific studies and assessments through the EIA process in order to delineate areas of sensitivity within the broader site, and ultimately inform the placement of the wind turbines and associated infrastructure.
Phased construction planned The construction of the facility is proposed to be a phased one, with the first phase of the project planned to generate about 100 MW. The sub- sequent phases would, however, not exceed 100 turbines for the total facility on the proposed site. The construction phase for the erection of about 50 wind turbines, as well as all the required associated infrastructure, is expected to take in the order of 24 months.
Network integration studies, planning, and design for the transmission of the power generated at the wind energy facility are still being finalised. But a 132-kV powerline is proposed to connect the substations at the wind-energy facility to the electricity distribution network at either the Koekenaap distribution substation, or the Juna transmission substation.
The connection point to the Eskom power grid will be confirmed through the network integration and planning exercise, and alternative routes for the powerline will be assessed in the EIA phase.
The planning report proposes that, owing to the nature of the plant and the process of construction, the facility also be commissioned in phases. The first phase proposes a facility with a generation capacity of about 100 MW.
Once operational, the wind farm will be monitored remotely. It is estimated that the operational phase of the project will provide employment for about six skilled staff members, who will be responsible for monitoring and maintenance, when required.
Each turbine within the facility will be operational, except under instances of mechanical breakdown, extreme weather conditions, or maintenance activities.
The turbine infrastructure to be deployed is expected to have a lifespan of 20 to 30 years. The equipment associated with the facility will only be decommissioned once it has reached the end of its economic life.
KLIPHEUWEL PILOT LED THE WAY
The proposed wind farm is not Eskom’s first foray into wind-generated electricity. The company’s pilot study was undertaken in 2002/3, when it erected three wind turbines at an experimental wind energy farm at Klipheuwel on the West Coast.
The objectives of the pilot programme were to measure the performance of the installed plant, identify issues that have a strong effect on the performance of the plant, and suggest mechanisms that could be applied to tackle these issues, and to assess the technoeconomic feasibility of various options, in an effort to improve wind generation in South African conditions.
The project has a total capacity of 3,2 MW, and was expected to generate at a load factor of between 15% and 20%. To date, more than 15 GWh of electricity has been generated, contributing to an avoidance of more than 14 000 t of carbon dioxide.
The three wind turbines operate at an average availability of 90%. The research, which was completed in 2006, was extremely successful. The project found that the best production occurs during the windy summer months, and the facility can operate between 10%, in the winter months, and 35%, in the summer months, depending on wind availability.
Twenty potential sites were originally identified, and the Klipheuwel site was chosen because of the acceptable wind speeds, its proximity to Cape Town for research and demonstration purposes, and an existing electricity distribution infrastructure.
The site was used to evaluate a variety of different wind technologies and storage systems, and to generate wind, cost, and performance data, which is essential for the design of future large-scale wind farms.
The Klipheuwel wind farm consists of three units, which are linked to one another by an 11-kV underground cable, which, in turn, is connected to Eskom’s 66-kV to 11-kV substations in Klipheuwel by a short overhead line.
The first unit came on line in August 2002, and the last was commissioned in February 2003. The turbines are auto-controlled and auto-dispatching, making it unnecessary to have full-time staff on site. Each wind gener- ator has its own small meteorological station on top of the turbine, as well as an aircraft warning light.
The wind turbines at Klipheuwel generate at wind speeds of between 11 km/h and 50 km/h, while full power is only reached at about 50 km/h.
The facility will be commercially operated for its expected 20-year lifespan by Eskom’s generation division.
STRIKING THE CORRECT BALANCE
The amount of energy a wind turbine can harness depends on both the wind speed and the length of the rotor blade. Wind speeds below about 13 km/h are insufficient to produce power, while powerful gusts can damage mechanical equipment.
Variation in the speed and inconsistence of the wind can constrain continuous operations. The cost and space required for a wind-operated power plant is still relatively high – for instance, Eskom estimates that a 300-km2 area of wind machines would be necessary to produce the same power generated by one large coal-fired or nuclear power station, assuming a consistent wind pattern of roughly 50 km/h.
But as the technology takes hold globally, the viability of harnessing the power of the air appears to be growing. The cost of wind turbines seems to have stabilised somewhat internationally. But it still has some way to go before it can compete with Eskom’s low-cost installed base. It is estimated that, in South Africa, wind energy will cost 65c/kWh, compared with about 23c/kWh from Eskom’s installed capacity.
POTENTIAL FOR 1 000 TURBINES
Eskom estimates a potential for wind-generated electricity around the coastline of South Africa at about 1 000 turbines, based on land avail- ability and accessibility, access to grid connection, and available wind.
As far as decisions on future wind projects are concerned, the uptake of renewable energy in Eskom’s mix forms part of its integrated strategic electricity planning process, and experiences gained at the demonstration facility will certainly feed into this. It should be noted, however, that future installation decisions would be made, based on the commercial feasibility of the proposed project.
But with space now being created for inde- pendent power producers in South Africa’s energy economy, what are the prospects for commercial wind-energy ventures? One such project is beginning to gain traction, with South Africa’s first commercial wind farm having been approved for the Darling district of the Western Cape, in March 2005.
Darling Wind Power CEO Hermann Oelsner tells Engineering News that the project entails the erection of ten 1,3-MW wind turbines, and will be undertaken in two phases.
Phase 1 involves the erection of the four turbines and is set to deliver a total output of 5,2 MW. Phase 2 will add a further six turbines to the mix, bringing the total capacity to 13 MW.
“As a whole, the Western Cape may have the potential to generate as much as 10 000 MW of wind power, so wind energy is the most feasible alternative energy source for this location,” he said. The ten turbines are set to save about 32 000 t of carbon dioxide emissions yearly.
A 20-year power purchase agreement was concluded with the City of Cape Town, in which consumers will be the first beneficiaries of the commercially generated green power. Consumers buying the green electricity will pay about 25c/kWh unit, above the normal cost of electricity.
A spokesperson for the Cape Town Municipality says that the latest targeted date for generation from the Darling wind farm is the middle of February 2008. “I believe the foundations have been cast, and I know that the wind turbine blades have been delivered. I believe that there are one or two items which were delayed, and I would imagine it was because of the global demand for wind turbines,” the official says.
FROM THE WEST COAST TO THE EAST
The consensus among industry participants is that the coastal areas of South Africa offer a better opportunity for wind energy, as opposed to the mountainous areas of the inland.
The wholly owned subsidiary of the Central Energy Fund, the South African National Energy Research Institute (Saneri), states that insufficient research has gone into South African wind conditions, and the optimum location for wind farms.
Saneri senior manager for clean-energy solutions Dr Thembakazi Mali says that most research into wind energy has been done under the high-speed wind conditions in Europe. “In the South African context, our prevailing winds are not as high, but instead are medium to low. So we have not actually got to a point where we can harness those wind speeds.”
She states that Saneri plans to research the wind conditions in and around South Africa to compile a bona fide wind atlas.
“The atlas that is currently available does not cover the entire country or the coastline, and the measurements were not taken at the appropriate heights.”
Saneri is hoping to undertake the research project in conjunction with the South African Weather Bureau. “If you think of the weather service, they have stations all over the country and they are ideally placed to acquire the readings we will need.”
Mali says that although the project is still in concept phase, it should take about three years from initiation to completion.
Having completed the atlas, Saneri will do further research into the components to build the wind turbines and their suitability for local production.
One of the hurdles to wind-energy generation, says Mali, is the lack of policy within South Africa. “I think there should be a lot of political will for the different statutory institutions to reach the targets that were set by government. There should be enough involvement and funding so that targets are met.”
Mali suggests that the framework policy and feeding tariff structure should be sped up. “There are a lot of people out there who are just waiting on a feeding tariff. There are small companies and individuals doing a lot of interesting energy- related projects. They have been generating renewable energy, but because they are not putting it into a grid, it is lost.”
In May, the DME released a feasibility report on the implementation of the Tradable Renewable Energy Certificates (Trecs) system in South Africa. The report states that a growing amount of activity in the private sector to produce and procure renewable energy, even within the admittedly restrictive and uncertain local policy and regulatory context and market parameters, is starting to require credible verification.
The concept of Trecs is based on separating the various attributes of renewable resource-based energy provision from the physical energy carrier.
The report states that there are three possible income streams for renewable-energy electricity generators, including power purchase agreements into the electrical grid at the prevailing electricity market price, certified emissions reductions trading through the Clean Development Mech-anism of the Kyoto Protocol, and the issuing of Trecs.
A significant advantage of Trecs, apart from the extra income stream, is that Trecs can be traded worldwide, and separately from the electricity grid infrastructure, thereby avoiding the complexities of use-of-grid system charges, or grid access problems.
Trecs provide a good opportunity for verification of financial support to registered renewable-energy generators, by both the public and private sectors, the report reads.
The most important motivation that has emerged in terms of national renewable-energy policy is the ability of a Trecs system, and associated infrastructure to provide a tool for the monitoring of renewable energy uptake independently of the choice of incentive or regulatory framework to be put in place to stimulate that uptake.
Monitoring, in turn, also provides feedback on the success of various policies and for the refinement of these, or the adoption of new policies and support mechanisms.
The report found that, in South Africa, the Trecs system should be based on the general framework of the Basic Commitment in Europe and should also make use of the elements of the Trecs systems of those countries that could add value or benefit, such as the Netherlands and Australia.
Under a voluntary Trecs system, the government’s role has predominantly been to create demand for Trecs through measures to stimulate and enforce renewable energy uptake. The Trecs system can then be incorporated as a tool in proving compliance with obligations, or in the administration of claiming production-based public financial support.
The recommendations emerging from the feasibility study are primarily that the European Basic Commitment should be adopted as the basis for a framework upon which to develop a South African Trecs system, and that a statement should be issued by the DME spokes- person affirming government support for tradable renewable energy.
The white paper on renewable energy has set a target contribution of 10 000 GWh of renewable energy to the final energy consumption, by 2013.
What is becoming more and more apparent is that there is a unique opportunity for the growth of a serious renewable-energy industry in South Africa, given growing security of demand and a desire to reduce the country’s carbon footprint. But what is also plain is that unless government and Eskom take an active role in its promotion, the full potential for renewables will not be realised.