Energy expenditure is a heavy burden for the current water supply system (catchment and potability) in the Barcelona and Girona region, especially in the current context of drought. It is one of the determining factors in the price of these resources. This is indicated by David Vila, director of the Ens d’Abastament d’Aigua Ter-Llobregat (ATL), a public company in charge of selling potable water to municipalities that account for almost 5.5 million people in Catalonia.
The strong dependence on the supply of the two desalination plants has turned the energy expenditure into one of the key factors in the increase in the cost of water purification treatments.
ATL, owner of the desalination plants in Blanes and El Prat, as well as the water treatment plants in Ter (Cardedeu) and Llobregat (Abrera), yesterday approved the review of tariffs for the 116 customers (municipalities), among which the Barcelona Metropolitan Area. The ATL water tariff will be 30% more expensive (which would be equivalent to close to 1 euro per month), although the final impact on the receipt of water remains to be determined, which depends on the tariffs that are approved the Metropolitan Area of ??Barcelona and the other municipalities.
The ATL water supply is already the second largest consumer of electricity in Catalonia, surpassed only by Renfe; and it is above that of Ferrocarrils de la Generalitat and the Catalan public hospitals. The forecast is an annual expenditure of 60 million with a consumption of 300,000 MWh. Under normal conditions, the desalination plants work at 25% or 30% of maximum output, while last year it worked at 100% due to the drought. The company ATL has also found itself with a new energy contract, which means that the price of electricity has risen by 50% since September. “In addition, the forecast is for the desalination plants to work at full capacity all year round”, says David Vila.
Currently, 33% of the resources supplied to the 23 municipalities served by Aigües de Barcelona come from the El Prat desalination plant. While the water from the Ter that is made potable in Cardedeu goes down in pipes by gravity to Barcelona, ??making it potable in the desalination plants involves high energy consumption (catchment at sea, membrane filters). In the first case, obtaining drinking water costs 0.05 euro cents per m3, while in the second (desalination) it costs 30 cents per m3. They are six times more. All this leads to greater use of reagents, more staff hours and more intensive use of facilities, to the point that what were previously special operating conditions will be considered structural measures next year.
In addition, the ATL must comply with the so-called Ter agreements, a pact that obliges to reduce water abstraction in this river. This means going from a transfer in Barcelona of 135 hm3 each year to 90 hm3, so that 45 more hm3 will need to be desalinated, with the consequent cost overrun, explains Vila.
Several experts suggest the convenience of using photovoltaic solar energy to offset the high electricity costs, even if only partially. One of the formulas is the large-scale use of self-consumption with photovoltaic solar energy, a formula that would allow prices of 45 to 50 euros per MWh and savings of almost 50%, as explained by Salvador Salat, co-delegate in Catalonia of the Photovoltaic Union (Unef), which brings together companies in the sector. Other experts point to the fact that this formula has limitations derived from the physical space they occupy.
The new desalination plant planned in Blanes will be accompanied by a 6 MW solar plant, but this will only contribute 12% of consumption. “Desalination plants are huge consumption monsters. To compensate for that of the new desalination plant in Blanes, an area of ??tens of hectares would be needed, an impossible fact in an area of ??high value such as the coastal area”, another expert points out.
Salat also proposes to take advantage of the moments of more solar radiation, and when the remuneration of the system is very cheap, to produce desalinated water and store it (“store kilowatt hours in the form of water”), even if this runs into physical space limitations in coastal areas.
Another option to take advantage of the cheapness of solar is to sign bilateral supply contracts (PPA, for the acronym in English) with solar photovoltaic energy producers (regardless of location), which would lead to a fixed price guaranteed in the long term time limit. In this case, the problem comes from the fact that the production of the desalination plants is very variable, so the alternative would be to provide for coverage with a usage ratio to specify the prices in the contract.
