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Network integration of renewable energy

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In this article by Aurecon’s Dr Clinton Carter-Brown, Deon Vrey and Rabagolo Melesi, and Eskom’s Ronald Marais and Kevin Leask, we explore strategies to connect the South African Renewable Independent Power Producer Procurement Programmes (REIPPPPs) with the national grid.

REIPPPP and the national grid

The procurement of Independent Power Producers (IPPs) in South Africa is being implemented in alignment with the National Development Plan (NDP), Integrated Resource Plan (IRP) and Ministerial Determinations. IPP procurement requires that the generated power be connected to the national electricity grid, where it is transported to consumers (loads) for consumption. The ability to procure IPPs is premised on a capable transmission grid that has sufficient capacity to evacuate the generated power. The REIPPPP is hence critically dependent on access to the national transmission grid.

The purpose of this paper is:

  • To provide context as to the progress and planned development of the REIPPPP
  • To communicate key learnings and recent developments in the roll-out of the REIPPPP’s within South Africa, as required for context as regards transmission grid connection dependency and capacity
  • To provide context as to the available transmission grid capacity for the connection of REIPPPP’s
  • To provide feedback as regards the development of a strategy and an associated summary of the transmission project funding requirements to provide transmission capacity to connect REIPPPP’s

Background

The first three Bid Windows (BW) of the REIPPPP have concluded commercial contracts with Sellers, and the projects are at various stages of commercial operation and development. 1.7 GW of generation is already in commercial operation. The BW4 Preferred Bidder allocation of 1121MW was made in April 2015, and the Minister of Energy also announced the intention to allocate additional MWs from the BW4 procurement process. Furthermore the Minister announced plans for an expedited procurement process of 1.8 GW of renewable energy.

The first three REIPPPP Bid Windows consumed much of the available transmission grid capacity in the Northern Cape, Eastern Cape and Western Cape. There is an urgent need to create additional transmission grid capacity for the REIPPPP.

Renewable generation resource location and development strategy

The following sections provide context to the potential locations of renewable energy sources, as well as assumptions as regards the strategic development of areas.

• Renewable Energy Development Zones (REDZ - Wind and Solar)

The Department of Environmental Affairs (DEA) has committed to contribute to the implementation of the NDP and IRP by undertaking Strategic Environmental Assessments (SEAs) which identify adaptive processes that streamline the regulatory environmental requirements and inform planning and design in a manner that safeguards the environment.  The wind and solar photovoltaic (PV) SEA was commissioned by DEA to provide strategic guidance and ensure that the future development of wind and solar PV projects in terms of SIP 8 is conducted in a sustainable manner.  As such, the SEA identifies areas where large scale wind and solar PV energy facilities can be developed in terms of SIP 8 and in a manner that limits the potential for significant negative impact on the natural environment, while yielding the highest possible socio-economic benefits to the country 1.

The areas put forward as proposed Renewable Energy Development Zones (REDZs) in the SEA (figure 1) have been identified through integrated spatial analyses and wide stakeholder consultation, and as geographical areas in which development is considered most appropriate from a national strategic perspective.  Factors taken into consideration include energy resource potentials, infrastructure availability, stakeholder and local authority support, environmental suitability and socio-economic needs. Since numerous suitable areas with exceptional wind and/or solar resource still exist outside the REDZs, every proposed development anywhere in the country must still be considered and evaluated on its own merits.

Figure 1 - Spatial Presentation of REDZ


Figure 1: Spatial presentation of REDZ 1

A category of transmission projects identified in this paper unlock grid capacity in these identified REDZs. The REDZ are presently confined to the Western, Southern and Central regions in South Africa, but are planned to be expanded to also cater for Solar REDZ in the Northern and Eastern regions. 

• Solar PV

Various options to the future allocation of PV farms in South Africa were developed in a GIZ led study 2. The aim of the study was to quantify the economic impact of different strategies (‘allocation strategies’) for the deployment of utility scale PV farms in South Africa. Three different allocation strategy scenarios for a total of 8.4 GW of utility scale PV farms in South Africa were considered:

  • Scenario A: “Maximum Energy Yield” This scenario is according to the existing applications for PV farms where there is a total of, 6.4 GW of PV in the Northern Cape, and 2 GW distributed elsewhere in the country.
  • Scenario B: “Close to load centers” Here, only 2.6 GW of PV is considered in the Northern Cape, the remaining 5.8 GW is distributed across the country.
  • Scenario C: “According to Renewable Energy Development Zones” For this scenario 2.8 GW is considered in the Northern Cape, and 5.6 GW is distributed predominantly in the REDZ.

The cost impacts of the three scenarios were expressed in levelised form on the basis of units of produced electricity from PV. These included the Levelised cost of electricity, Levelised cost of transmission grid upgrades (per kWh of generated PV electricity), Levelised cost of distribution grid upgrades (per kWh of generated PV electricity) and Levelised cost of electrical transmission losses (cost of losses per kWh of generated PV electricity).

Figure 2:  Spatial presentation of Solar Potential

Figure 2: Spatial presentation of Solar Potential

The following GIZ study outcomes need to be considered 2:

  • The overall costs of the three scenarios are very similar. Decisions with respect to the future strategies for allocating PV farms in South Africa should consider additional criteria such as the risks associated with each allocation strategy. Specifically, the timely realisation of transmission grid upgrades is considerable. Therefore Scenario B and Scenario C (more heavily distributed PV) is more favorable as compared to Scenario A (large concentration of PV in the Northern Cape requiring significant transmission upgrades).
  • Consequently, the most economical approach will be to use the available transmission grid capacity in the Northern Cape up to its full extent for PV generation. This limit is estimated at 2.8 GW of installed PV capacity, and is still subject to grid infrastructure upgrades so that the full 2.8 GW can be realised.
  • PV capacity above this 2.8 GW limit should be distributed across the country. Besides solar irradiation/energy yield, other criteria such as required transmission and distribution upgrades, socio-economic impact, environmental impact etc. should also be considered when deciding upon the spatial allocation of these generators.

The study further concluded that future rules and regulations in South Africa, especially those relating to the REIPPPP, should consider these aspects in order to ensure the most successful and cost efficient deployment of utility scale renewable PV generation.

• Wind

Power production from wind is highly sensitive to wind speed, which varies considerably across the country (Figure 3), and is influenced by localised climatic conditions. As such wind power will be confined to areas with high average wind speeds. The spatial distribution for future wind power plants will be such that grid capacity needs to be created in the areas with high average wind speeds. The consideration of suitable wind generation areas was a key consideration in the development of the REDZ 1.

Figure 3 - Spatial presentation of wind resources (Wind Atlas South Africa)

Figure 3: Spatial presentation of wind resources (Wind Atlas South Africa)

Transmission network capacity

A key challenge in the procurement of utility scale renewable energy is the cost and timeline for the creation of grid capacity to connect the REIPPPPs to the national grid. The location of the generation plants in relation to the grid is important, and directly impacts on grid connection scope, cost and timeline. The proximity of the new generation plant to the existing grid is on its own is not an indicator of grid capacity as the existing grid may be constrained, with little or no capacity to accommodate additional generation.  Grid constraints are becoming more prevalent as the IPP Programmes progress and the limited spare capacity (in areas with good resources) is depleted.  Grid connection will continue to be an increasing challenge in future bid windows. Proactive plans are required to procure grid capacity in alignment with the spatial generation plans of the country.

In support of understanding the short-term available transmission capacity, Eskom Transmission has published the Generation Connection Capacity Assessment of the 2016 Transmission Network (GCCA-2016) to communicate the grid’s capacity to connect all types of generation plant at high-voltage (HV) bus bars of the Main Transmission System (MTS) substations in 2016 3.

Figure 4 - Spatial presentation of GCCA-2016

Figure 4: Spatial presentation of GCCA-2016

Figure 4 (above) illustrates the spatial representation of the network capacity to connect generation as informed by the GCCA-2016. The scale of “red – orange – yellow – lime – green” is used to graphically show the range of available network capacity per transmission substation zone:

  • The red areas indicate substations that are over-subscribed and network upgrades are already essential. No further generation can be connected.
  • Orange and yellow areas indicate substations with limited capacity (0 to 400 MW). Limited additional capacity can be connected, and upgrades can be anticipated.
  • Green areas indicate substations with capacity in excess of 400 MW. Significant amounts of additional generation can be connected with no transmission grid upgrades.

In general the country is dominated by the red to yellow colour range, indicating a constrained transmission grid, particularly in the Western, Northern and Eastern Cape.

The analysis and findings that follow are based on the transmission grid capacities as published in the GCCA-2016.

REIPPPP grid connection assessment

Based on the existing transmission grid capacity and generation resource location, an analysis was performed to assess the likely grid constraints and associated upgrades (scope, cost and timeframe). The analysis was performed using the GCCA-2016 3 capacity values still available in the three Cape provinces and a range of potential transmission phased strengthening options identified by Eskom 4.

In order to identify the likely location of future renewable energy projects (and the associated potential network constraints) the REIPPPP BW4 submissions were used as a basis for assessing grid upgrade requirements. BW4 submissions were superimposed on the GCCA-2016 capacity layer, as illustrated in Figure 5. It illustrates that most of the BW4 submissions (in tourmaline green colour) are located in the GCCA-2016 red and orange areas, where there is limited or no grid capacity to connect the IPPs.

Figure 6 shows the impact of the BW4 submissions on network available capacity if all bids are connected with no further grid reinforcement.  As shown in Figure 6, the network capacity diminishes in areas where BW4 submissions are clustered (depicted by the more widespread reddish colour). Note the increase red and yellow shadings in Figure 5 as compared to Figure 6.

Figure 5 - Spatial presentation of GCCA-2016 with BW4 submission locations 

Figure 5: Spatial presentation of GCCA-2016 with BW4 submission locations

Figure 6: - The impact on Grid Capacity after connection all BW4 Interest, no further transmission grid reinforcement 

 

Figure 6: The impact on Grid Capacity after connection of all BW4 interest, no further transmission grid reinforcement

Preliminary transmission projects were identified to unlock the constrained networks via the implementation of the following project types (note that the project lead times are indicative, and with mitigation there is scope to reduce these timeframes):

  • Project Type 1: Addition of transmission feeder bays at existing transmission substations. Feeder bays do not necessarily add capacity to the network, however feeder bays are required for the integration of IPP’s. The estimated lead time to develop these projects is 2 years.
  • Project Type 2: Addition of transformer capacity at existing transmission substations. The estimated lead time is 3 – 4 years.
  • Project Type 3: Construction of new transmission substations, with no or little EIA requirement for transmission lines (substations located in close proximity to existing transmission line). The estimated lead time is 4 – 5 years.
  • Project Type 4: Construction of new transmission substations where new transmission lines are required and require an EIA. Estimated lead time is 6 – 8 years.

A structured process was followed to unlock the constrained networks in order to integrate the renewable IPP’s using the following staged approach:

  • Stage 1: Identifies the short term projects (3 – 4 years lead time) to provide capacity in the areas where BW4 submissions are clustered.
  • Stage 2: Identifies medium-term projects (maximum lead time of 8 years) to further increase capacity in the areas where BW4 submissions are clustered.
  • Stage 3: Identifies strategic grid projects to unlock the REDZ.

Note: The above stages do not include the development of any sub-transmission network expansion, nor any major corridor upgrades as may be necessitated by the combined impacts of the various IPP programmes.

Figure 7 illustrates the impact of the Stage 1 projects (Project Types 1 and 2), creating capacity in the short term (3 – 4 years) to connect BW4 IPP submissions. Note the change in the Western Cape from red/orange in Figure 6 to green in Figure 7.

Figure 7: Stage 1 - Short term projects to unlock capacity to connect BW4 submissions

Figure 7: Stage 1 - Short term projects to unlock capacity to connect BW4 submissions

Stage 1 projects add 4 000MVA of additional grid capacity at an estimated cost of R 1.6 billion (4 year timeframe).

Figure 8 illustrates the impact of the Stage 2 projects (Project Types 3 and 4 in the non-REDZ zones) that create capacity in the medium term (6 – 8 years) and further integrate BW4 IPP submissions. Note the change in the Northern Cape from red/orange in Figure 6 to yellow/green in Figure 8.

Stage 8: Stage 2 - Projects to further unlock capacity to connect BW4 submissions

Figure 8: Stage 2 - Projects to further unlock capacity to connect BW4 submissions

The Stage 2 projects further increase the network capacity by an additional 3 500 MVA at an estimated cost of R3.3 billion over the period of 6 – 8 years.

Furthermore, to strategically unlock the REDZ, Stage 3 projects were developed (Project Types 3 and 4 in the REDZ zones). The additional impact of the Stage 3 projects is illustrated in Figure 9. Note the change in the Eastern Cape from red/orange in Figure 6 to green/orange in Figure 9. The Stage 3 projects provide capacity in the REDZ given that there is limited grid capacity in these areas.

Stage 3 projects add 10 000 MVA additional connection capacity on the network to unlock the renewable energy development zones in the medium term (4 – 8 years) timeframe.  The cost to unlock such network capacity is estimated at R13.1 billion. It must however be cautioned that additional corridor strengthening may be required to evacuate this capacity, and the costs associated with such are being assessed.

Figure 9: Stage 3 - Projects to unlock the REDZ

Figure 9: Stage 3 projects to unlock the REDZ

The total cost to unlock 17 500 MVA network connection capacity for the REIPPPP is estimated at R18 billion.  Note, that this cost does not include sub-transmission network strengthening, or transmission corridor upgrades that may be required. Further analysis is underway to develop an implementation strategy whereby the project phasing, dependencies and costs can be optimised in support of the present and expected ministerial determinations for generation procurement. This necessitates integration of the IPP grid integration requirement in the Transmission Development Plan (TDP) and the distributor NDPs.

Conclusions and next steps

The grid upgrade costs identified in this paper need to be considered in the context of the following:

  • There is limited transmission grid capacity for REIPPPP connection, and grid upgrades and investment is essential to support the sustainable procurement of IPPs. This is supported by the experiences in the procurement of REIPPPP BW3 and BW4.
  • The lead-times of the transmission upgrades are such that the associated grid projects need to be proactively identified and initiated in advance of IPP procurement.
  • The network capacities, timelines and upgrade costs in this paper are based on information provided by Eskom.
  • The grid upgrade scope and cost estimate is confined to the transmission grid upgrades, as required to provide transmission connection capacity.

In order to obtain a more holistic understanding of the grid costs the following also need to be considered/included:

  • Transmission corridor upgrades to evacuate power along the major routes to the load centres.
  • The sub-transmission network expansion and upgrades to connect the individual IPPs to the main transmission substations.
  • The projects have not yet been optimised or phased to provide a logical, defendable implementation plan that can be funded and procured. This is the focus of further and ongoing work.

The following further work is underway:

  • The capacity, timing, scope and cost implication of transmission corridor upgrades also needs to be considered and included.
  • A prioritised transmission plan needs to be developed to the necessary level of detail as is required to secure funding and initiate the procurement of grid upgrades in a phased manner that aligns with REIPPPP programme timeframes, design and capacity needs.
  • A phased capital expenditure plan must be developed, whereby upfront investments can be initiated to obtain the necessary consents and secure servitudes, as well as undertake the associated detailed engineering designs. This will dramatically reduce grid project lead-times and risks.
  • This work needs to ensure integration with the National Planning Commission, SIPs, IRP and Eskom Transmission Development Plan.
  • The IPP Office is working closely with Eskom to ensure that the IPP grid connection requirements are directly considered in the update of the TDP, and are integrated with capital expenditure planning, approvals and budgets.
  • Furthermore the IPP Office is considering opportunities to optimise the REIPPPP programme design to better align with the realities of a constrained transmission grid and the requirement to accelerate the REIPPPP programme.

This article was published in Energize - June 2015, and is republished here with permission.

References

1. “Strategic Environmental Assessment for Wind and Solar Photovoltaic Energy in South Africa”, 2014, developed by the CSIR for the Department of Energy, Environmental Affairs.
2. “Analysis of options for future allocation of PV farms in South Africa”, 2014, developed by GIZ for the Department of Energy.
3. “Generation Connection Capacity Assessment of the 2016 Transmission Network (GCCA-2016)”, June 2014, Eskom
4. “Proposals for unlocking the Transmission Grid for increased IPP Connection Capacity Rev1”, September 2014, Grid Planning, Eskom

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