Electricity production from renewable energy source (RES) has been rapidly growing for the last decade, bolstered by an increasing technological maturity and a political willingness to foster a transition towards a low carbon society. Until recently, the integration of the limited amount of intermittent RES production (photovoltaic, wind) into the power of grids didn’t induce major problems: the production flexibility of centralised units was sufficient to balance the intermittent RES output. Nowadays, the integration of a steadily increasing intermittent power in the power grid arouses more and more stability issues for both TSO and DSO.
The electrical system will have to evolve profoundly in terms of physical infrastructures and market organisation to support further developments of the renewable energy production. The prevailing "fit-and-forget" paradigm (decentralised production units statically managed units) must be transformed into a more active, dynamic and decentralised organisation paradigm. The distribution grid will be at the forefront of this evolution as it hosts an important part of the RES units and currently lags behind the transport grid in matter of regulation tools and market mechanisms. Infrastructure upgrades, better network interconnection and smart demand-side management will surely be parts of the solution. However, they may prove to be very expensive and/or slow to deploy in some contexts. The integration of a small or medium size energy storage component in the global energy system may definitively bring an interesting contribution to the solution to the energy balancing problem.
The objective of the
SMARTWATER project is to determine whether the rehabilitation of end-of-life quarries and mines into medium-sized PHES units can bring an economically viable contribution to the above-mentioned problem of power balancing. The project implements a holistic approach encompassing legal, environmental, economic, hydraulic, electro-mechanical, and geological aspects. The reservoir capacity and hydraulic head of most of the sites under consideration are around a few hundreds of thousand cubic meters and a few dozen meters respectively.
Accounting for 99% of the installed capacity, PHES is by far the most widespread technology among the interesting candidate approaches to electrical storage (batteries, Compressed Air Energy Storage - CAES, Supercapacitor, flywheel, Molten salt, superconducting magnetic energy storage- SMES, synthetic natural gas, ...). The PHES technology does not suffer of real technical bottleneck and can provide adequate solutions for a large power range and water heads between 10m and 1000 m. In addition, the innovations of this last decade in the field of reversible pumps coupled with variable speed rotors and controllers offer a greater level of flexibility and paves the way to innovative exploitation strategies dynamically mixing arbitrage, local power production and consumption management and provision of ancillary services. Small and medium size (between 1 MW and some dozens of MW) systems considered in the project could support the power balancing and grid stability not only at the transport level through established mechanism (such as capacity reserve, black start or frequency control) but also at the distribution level through emerging mechanisms
The PHES can also be credited of numerous other advantages including high technological maturity and robustness, virtually no emission of greenhouse gas and an excellent energetic balance over the lifetime (an issue for batteries) and no residual environmental impact (fully-dismountable facility). PHES definitively ranks high the list of the most environment-friendly energy storage solutions. The main disadvantages of PHES approach are the reliance on favourable topological conditions and the highly variable cost (preparatory groundwork, reservoir, powerhouse, hydraulic equipment, connection to the road and electrical networks, building permit, environmental impact evaluation, ...) of the facility according the site configuration (topology and geology).
The assessment of the economic feasibility requires the evaluation of both the facility costs and cash flows (operating costs and revenue streams). In the context of the project, both aspects are site-dependent. Adding to the challenge, sites under consideration are significantly different from existing facilities so that common references and good practices in the industry should be questioned. Reservoir, hydraulic head and storage capacity are smaller. These limitations for scale savings in the construction work can be offset but numerous and significant cost reductions such as existing reservoirs (flooded pits), existing access to the road and power network, low-cost pipes thanks to a lower pressure,… Interaction with the underground water compensates the lower reservoir losses but sets operating constraints. The evaluation of financial revenues from arbitrage activities, provision of ancillary services, local production and/or consumption power flow management and optimization of the investment planning (at the distribution and transport levels) vary widely according to the site location and because of rapidly evolving market conditions with different national regulation and steadily increasing intermittent RES production.
The project aims at developing various tools and models to tackle these numerous and unanswered questions. The work program is structured in 7 thematic packages:
- Legal (how to modify existing legislation ?) - environmental (how to control or mitigate environmental impacts?) and economic (how to monetize the storage, on which kind of services ?) environments for the use of PHES in those innovative sites in Wallonia.
- Tools for long term and day-ahead planning of storage capacities.
- Both simulation tools and deployment guidelines of electro-mechanic systems and its connectivity to the DSO network using specific approaches based on exploitation of static electronics converters.
- Both simulation tools and deployment guidelines of hydraulic pumps / turbine with specific emphasis on usage of reversible variable speed turbo machines based on customization of "on the shelf" existing pumps.
- Both simulation tools and deployment guidelines of Geological storage sites: inventory in Wallonia, geo mechanic, hydro geologic and hydraulic simulations tools to evaluate the potential of any PHES site.
- Global (Economic, geological, technical efficiency impact) System level simulation tools able to identify the potential impact of any parameters in the system
- Development and test of analysis tools (except geological) on an fully instrumented small dimension test-bed connected to an integrated micro network (50 KW PV, 10 KW wind turbine, 10 KW batteries, real demand side users). Hydro geo mechanical models of several existing sites will be also included in this package
Project keys parameters
Budget : 3.7 M€ ( grant = 3.1M€ - excluded use-case infrastructure installations)
Financial Sponsoring by SPW-DGO6 - Service Public de Wallonie - Research Department
Duration : 2+1 years - 1 Sept 2014 › 1 Sept 2017
Integrated project with 3 R&D orientations: technological, socio-economical,environmental and geological
20 partners & sponsors - 9 industrials (1 environmental consultant (ECOREM), 2 quarry site owners (Carmeuse & CBR), 1 pumps manufacturer (Ensival-moret), 1 DSO (ORES), 1 TSO (ELIA), 1 energy producer (ENGIE-LABS), 1 energy trader (ENGIE), 1 system integrator (ENGIE-FABRICOM)) - 2 Applied R&D (MULTITEL &ISSEP ), 7 academics (ULG-HGE, UMONS-GEO, UMONS-GELE, ULG-HECE, ULG-GGI, ULB-ATM & UCL-CEREM ), 2 public bodies (IDEA & IDETA)