TERMOSOLAR: Mantenimiento Centrales termosolares

Although fuel consumption is theoretically zero, generate electricity in a solar thermal power plant requires a high operating and maintenance budget. Appropriate consideration of each budget ensures high availability and long life. In contrast, a tight budget, multiply the number of breakdowns and unplanned shutdowns and makes installation deteriorates rapidly.

The solar thermal power plants of parabolic trough concentrator (CCP) and solar thermal plants 50 MW of power that are being implemented in Spain since the end of 2008 and can go as far between 1,500 and 4,000 MW of installed capacity, will be a major challenge for those responsible for maintenance of these plants. What budget will tell? What amount of money is necessary to provide for the proper maintenance of these facilities?

The first major budget item is related to labor. The team needed to address the maintenance will be between 15 and 20 people, including indirect staff (managers and technical office), the direct personnel (personal mechanical, electrical and instrumentation), the cleaning staff (both industrial and mirrors), own permanent staff and contract personnel. The total equipment Operation and Maintenance is around 45 people, so maintenance is approximately 40% of the workforce.

In order to measure the consumption of parts is convenient to divide the plant in systems and analyze each separately. We must take into account the warranty period because during this time consumption is far below the normal budget after finishing this period and the equipments suppliers will have to take care of the necessary materials for repair failures which have their origin in premature fault.

- Consumption of spare in the solar field. The solar field includes two major consumer materials: mirrors, fragile element that break easily, and the absorber tubes, which is a thin cover glass. It is also necessary to provide for the maintenance of hydraulic power units and cylinders required fo the movement of the collectors (in a plant is installed between 350 and 650 of these hydraulic units).

- Consumption of spare HTF system. Should be taken into account that this system includes the equipment more sensitive and prone to failures: drive pumps thermic fluid. These pumps have a sensitive element, closures, and if the selection of the pump has not been careful replacement cost of these closures may have a strong impact on the maintenance budget. There is a important consumable the thermal oil. Keep in mind that plant needs to replenish daily between 200 and 500 kg. of hot oil, in addition to possible leaks, and the thermal oil life is limited (about ten years).

- The thermal storage system (TES). Vertical pumps are a delicated point of this system.

- The water-steam cycle (WSC). It will be necessary to consider the small material, as the valves, seals and gaskets generally involve a high percentage of materials budget. The water-steam cycle includes some important consumables: the chemical products of the cycle.

- The steam turbine. The annual budget for consideration is small, through it must be noted that the turbine requires a major revision every 3-5 years, of high cost.

- Generator. It is generally reliable equipment, thus spare normal comsumption is very low.

- The BOP (Balance of plant). As water-steam cycle, sealing parts, consumable items, pumps and valves represent a significant percentage of maintenance costs. In addition, the BOP includes a consumable important: chemicals in the water treatment plant, the treatment plant effluent and the cooling towers.

- The high voltage system. They are reliable equipment, thus requiring a low budget.

- The low voltage electrical systems. Spare consumption is higher that that of high tension, especially small items.

- Instrumentation. The budget of sensors, transmitters and signal conditioning cards is significant.

The annual budget devoted to spare in 50 MW thermal power plant is well cared for an amount that will be between 1 and 2 million/year, assuming 1,5 million with an average item may be adequate in most cases. To that amount must be added consumables that have been advanced, and highly dependent on the operation carried out on the ground. Briefly, these consumables are:

The amount involved in all these consumables is highly variable and range between 1 and 2 million €.

There are a number of subcontratos to be taken into account. The most important is the maintenance of steam turbine, which will have two major items: the annual contract services and the cost of major revision or overhaul. These costs vary greatly depending on the manufacturer of the turbines and how to address the maintenance of this equipment.

Another very important item will be the legal maintenance, this is, the maintenance taht must be done by requirement of some legislation. The certifications and the contracting of these services suppose a significant item.

Other subcontracts to consider are the following: recruitment of additional staff for specific periods, maintenance service contracts with manufacturers of certain equipment and cleaning contracts. subcontratos a tener en cuenta son los siguientes: contratación de personal adicional para puntas de trabajo, contratación de servicios de mantenimiento con fabricantes de determinados equipos y contrata de limpieza.

In addition to the initial heading, which is usually included as an initial investement of the plant, should be considered a replacement item tool and acquisition of new means. This item may be around 150,000 € per year. The rental of lifting equipment and of scaffoldings is a really important item, because most plants do not have adequate systems. The budget can be around an annual amount exceeding 150,000 €.

The summary of the total maintenance budget can be indicated in the table below. Remember that these amounts should be taken as a simple reference, and that each case has to be calculated with the rigor and the necessary care.

In the business plans of some thermoelectric power plants has been estimated a budget insufficient to meet the maintenance of the plant. Keep in mind that in this type of power plant, systems are complex and problematic, as the system HTF or water-steam cycle. As has happened in other energy facilities, such as plan biomass or CHP (cogeneration), to consider a budget lower than necessary for the proper maintenance of power generating plant represents a reduction of the availability, of the income by production and a rapid deterioration of the plant, which is a premature aging thereof. The correct consideration of the items for maintenance in the design phase is the best guarantee that the maintenance of these plants is carried out with the necessary rigor.

Solar Thermal Power Plants Maintenance