Energy expenditure is a heavy burden on the current water supply system (capture and purification) in the region of Barcelona and Girona, especially in the current context of drought. It is one of the factors that are determining the increase in the cost of these resources. This is indicated by David Vila, director of the Ter-Llobregat Water Supply Entity (ATL), a public company in charge of selling potable water to municipalities that represent almost 5.5 million people in Catalonia.
The strong dependence on the supply of the two desalination plants has made energy expenditure one of the key factors in the increase in the cost of purification treatments.
ATL, owner of the Blanes and El Prat desalination plants as well as the Ter (Cardedeu) and Llobregat (Abrera) water treatment plants, yesterday approved this rate revision for its 116 clients (municipalities), including the Barcelona Metropolitan Area. The ATL water rate will increase by 30% (which works out to between 1 euro per month), although the final impact on the water bill remains to be determined, which depends on the rates approved by the Barcelona Metropolitan Area and the others. municipalities.
ATL's water supply is already the second largest consumer of electricity in Catalonia, only surpassed 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 in the last year they have worked at 100% due to the drought. ATL has found itself in parallel with a new energy contract, which means that since September of this year the price of electricity has risen by 50%. “In addition, the forecast is for the desalination plants to operate 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 drinkable in Cardedeu goes down in gravity pipes to Barcelona, the water treatment in desalination plants entails high energy consumption (capture in the 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 of this entails 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, ATL must comply with the so-called Ter agreements, a pact that requires reducing water intake in this river. This means going from a transfer to Barcelona of 135 hm3 per year to 90 hm3, so another 45 hm3 will have to be desalinated, with the consequent extra cost, explains Vila.
Various experts suggest the convenience of resorting to the use of photovoltaic solar energy to offset these high electrical costs, even 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%, according to Salvador Salat, co-delegate in Catalonia of the Photovoltaic Union. (Unef), which brings together companies in the sector. Other experts point out that this formula has its 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 alone will contribute 12% of consumption. “Desalination plants are huge consumption monsters. To compensate for the new Blanes desalination plant, tens of hectares would be needed, something impossible in a high-value area like this coastal area”, says another expert.
Salat also proposes taking advantage of the moments of maximum solar radiation, and in which the remuneration of the system is very cheap, to produce desalinated water and store it (“storing kilowatt hours in the form of water”), although this comes up against the limitations of physical space. in coastal areas. Another option to take advantage of lower solar prices is to sign bilateral supply contracts (PPAs) with solar photovoltaic energy producers (regardless of their location), which would entail a guaranteed fixed price in the long term. The problem here is that the production of the desalination plant is highly variable, so the alternative would be to provide coverage with a usage ratio to specify the prices in the contract.
