| Work Detail |
Most studies of European 100% renewable energy overlook pumped-hydro energy storage (PHES), for the following, incorrect, reasons: there are few PHES sites; more dams on rivers are required; large areas of land are flooded; large amounts of water are required; there is a heavy environmental cost; and the capital cost of PHES is high. All these perceptions are wrong. With its northerly latitude, winter solar availability in Europe is poor. In winter, a decarbonized Europe will rely mostly on solar energy generated in the south and wind energy in the north. Large-scale long-duration energy storage is needed to ride through days or even weeks of poor solar and wind availability. Fortunately, Europe has unlimited, low-cost, off-the-shelf, low-environmental-impact, long-duration, off-river pumped hydro energy storage (PHES), that requires tiny amounts of land and water and does not require new dams on rivers. Pumped hydro-energy storage PHES provides about 95% of global long-duration (hours-days) energy storage (GWh). Batteries provide short-term storage (a few hours) with high-power (GW). Together, PHES and batteries solve energy storage. The global pumped hydro atlas lists 820,000 sites in the size range of 2-5000 GWh with a combined storage of 86 million Gigawatt-hours. This is equivalent to 2 trillion electric vehicle batteries. The atlas includes premium sites (cost-class AAA and AA), and lower quality sites (cost classes A, B, C, D and E). Premium PHES sites are characterized by large head (>500m), low-volume dam walls, short pressure tunnels, large-scale (>40 GWh) and long duration (>100 hours). Europe has over 6000 premium PHES sites with a combined storage of about 1100 terawatt hours, which is about 40 times more storage than required for a fully electrified and decarbonized Europe. There are also many lower-quality sites (classes A-E). The capital cost of premium-quality long-duration PHES is in the range of $8-25 per kWh. For example, Snowy 2.0 PHES in Australia (class AA) costs about A$12 billion for 350 GWh of energy storage and 2.2 GW of storage power (160 hours duration). This corresponds to US$22/kWh, which is far lower than batteries for a system that will last 100 years. Clean hydrogen has been considered for long-duration energy storage. This is inhibited by the low round trip efficiency of electricity-hydrogen-electricity, and the high cost of electrolysis. However, large volumes of clean hydrogen are required to produce chemicals and synthetic aviation fuel, which can effectively store energy within themselves. Unlimited PHES Most studies of European 100% renewable energy overlook PHES, for the following (incorrect) reasons: there are few PHES sites; more dams on rivers are required; large areas of land are flooded; large amounts of water are required; there is a heavy environmental cost; and the capital cost of PHES is high. All these perceptions are wrong. No new dams on rivers: PHES has traditionally been associated with dams on rivers. However, most PHES sites are located away from rivers (“off-river”), for the simple reason that most of the landscape is not near a river. Europe has excellent PHES potential in Norway, in the Alps, and in the south. However, northern Europe lacks good sites. Fortunately, high-voltage transmission allows the sharing of both energy and storage across Europe. Strong transmission networks smooth out the effects of local weather and thus reduce storage requirements. |
