| Modernisation
● Maximise basin crop yields from irrigation and hydro-ecological benefits. Power systems typically treat water as a fixed input while water models allocate water to hydropower without considering energy system needs. Identifying advantageous integrated water-energy systems involves both a technical component and a “political” component, where stakeholders can judge for themselves the acceptability and balanced outcomes of different investment or operational interventions.
A country scale case study – Ghana We consider the case of Ghana, where growing energy
and water demands encourage a rethink of how the integrated system works. Whilst some FutureDAMS case studies considered where to build new dams and how to size them, this particular study asked the question how could existing hydropower dams nationally be re-operated to enable more low-emission solar and wind (intermittent renewables) generation. Figure 3 compares many optimised water-energy infrastructure portfolios in Ghana; only six performance metrics are considered for simplicity. The interactive plot allows imposing limits on any of the metrics (eg minimal load curtailment, or maximum acceptable CO2
emissions
from the energy system as a whole, or from new assets). This helps identify sets of infrastructure assets that meet certain requirements and demonstrates their potential impacts on other sectors. Depending on the case study, various numbers of metrics will be tracked. The parallel axis plots like the one shown in figure 3 can display between two to dozen metrics, although most studies consider three to 10. Additional metrics can be added at the request of stakeholders provided the performance measure can be evaluated by the multi-sector simulator.
Understanding This approach can optimise investment in future
assets but can also investigate changes needed to the operation of existing hydropower assets as grid energy demand changes with increasing penetration of renewables. The hydropower industry is already promoting pumped storage facilities as a way of storing off-peak or spilled power from intermittent renewables. However, for countries with large hydropower systems, such as the 1020MW Akosombo Dam in Ghana, the potential impact on daily operations is also considerable. Reoperating a large hydropower dam will disrupt other
water users in the basin as base load and the current seasonal influences are replaced with a more daily and erratic hydrological regime as hydropower complements intermittent renewables. Understanding how more variable operation affects other water users, and what limits this may impose on hydropower’s flexibility, will become a critical part of hydropower operators’ tool kits. The FutureDAMS system evaluation and design
approach illustrates how changing dam operations may impact other water users within the Volta basin in Ghana. As is to be expected, 80% penetration of renewables leads to significant hydro-ecological alteration (see figure 4).
Future work The methods developed in FutureDAMS’ multi-sector
assessment linked to strategic (optimised) design and trade-off analysis, allows hydropower planners and investors, river basin agencies and country ministries
Flexible
Figure 3. Optimised designs of Ghana’s detailed national water-energy system. Each line represents the current system with any number of new interventions, in this case energy generation infrastructure investments and hydropower operational policy changes. Better performance is plotted higher up, so a perfect portfolio of interventions would be a flat line across the top of the plot. The hundreds of grey lines show the difference levels of performance achieved by the best performing (optimised) portfolios of water-energy interventions. The green lines show a selected subset of intervention scenarios that minimise hydro-ecological alteration and which include no new transmission lines. This plot is available as a web-based interactive plot (
polyvis.org). It allows different filters to be set (small grey boxes) to investigate which interventions allow achieving which levels of performance. The large black boxes highlight that using dams as currently to generate baseload power leads to high load curtailment (insufficient energy production) and an adoption of intermittent renewables of only 37% of the maximum amount
to get more benefits out of interlinked river basin- energy systems and reduce conflicts between water users and with the environment. The use of new online collaborative tools and interactive web-based graphics can facilitate effective and efficient engagement with interested stakeholders. Today’s tools are a step change from what was
available in the past; but tools alone cannot change how human-natural systems evolve. Much work remains to be done on how to integrate such approaches into planning and governance processes and embed them within institutions. Because the incentives are high, and the challenges (climate change, increasing access to electricity, achieving net zero) severe, there is considerable incentive to expand the use of the strategic design approach described here. This can only be achieved through industry, policymakers and planners working collaboratively to maximise the opportunities presented by interconnected energy and river basin systems. ●
Annual load curtailment [%]
Emissions [Mton CO2
e]
Operating costs [M$/yr]
ecological alteration Akosombo
Hydro-
Annual load curtailment [%]
Emissions [Mton CO2
e]
Operating costs [M$/yr]
ecological alteration Akosombo
Hydro-
Intermittent renewable [MW]
Transmission lines
expansion [MW]
Figure 4. Parallel axis plot showing that portfolios with lots of new intermittent renewable energy generation (80% of maximum intermittent renewable capacity) and no new transmission lines are associated with poor hydro- ecological performance. The plots show the consequences of re-operating the Ghanaian water-energy system solely for emissions reduction and ignoring hydro-ecology
Intermittent renewable [MW]
Transmission lines
expansion [MW]
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