Concentrated Solar Power

Question 1

How does CSP works?

Answer 1

Unlike PV systems, Concentrated Solar Power plants require direct solar irradiation (DNI = Direct Normal Irradiation). Mirrors are used to concentrate the sun’s rays on a fluid that is converted into steam and drives a turbine, thus
producing electricity. Regions with high DNI are equator +/- 35°. DNI should be at least 1900 kWh/m2/y.

Question 2

What does DNI stands for?

Answer 2

Direct Normal Irradiance is the amount of solar radiation received per unit area by a surface that is always held perpendicular (or normal) to the rays that come in a straight line from the direction of the sun at its current position in the sky. Typically, you can maximize the amount of irradiance annually received by a surface by keeping it normal to incoming radiation. This quantity is of particular interest to concentrating solar thermal installations and installations that track the position of the sun.

Question 3

What does CPV stands for?

Answer 3

Concentrated Photovoltaic: Only electricity is produced, no steam generation or thermal storage

Question 4

For what other purpose than power generation could CSP be used?

Answer 4

Thermal storage

Question 5

What are the two main objectives of storage on CSP plants?

Answer 5

1. Firming the capacity, smooth the variability of solar input to provide consistent output
2. Time-shifting: supply when demand is high, store when demand is low

Question 6

What are the two main storage configurations combined with CSP?

Answer 6

1. Indirect storage systems: need for additional heat-exchanger, usually oil-based
2. Direct storage systems: storage tank directly included in primary circuit, usually molten salt

Question 7

What are business development aspects for installing CSP for example?

Answer 7

1. Experienced partners is key to enter the market
2. Support in specific country
3. Local content required
4. First-in-kind = high development costs => Standardisation will drive down cost
5. Difficult to measure DNI
6. Thermal storage increases utilization and reduces LCOE
7. Flat area, minor slopes accepted

Question 8

What are some operational challenges of CSP plants?

Answer 8

1. Operational stability issues, difficult to cope with transient operation (passing clouds) => thermal buffers more robust
2. High wind loads, outer mirrors more robust to act as windshield
3. Attracting of birds in receiver towers, blinding airplane pilots

Question 9

What are some maintenance challenges of CSP plants?

Answer 9

1. Reflectivity of mirrors ~ performance => regular cleaning required by wash trucks or even robots
2. When thermal oil used has heat transfer fluid (HTF), risk on fire and explosion when it makes contact with molten salt
3. In parabolic installations the HTF moves through movable pipes => serious risk of leakage

Question 10

How can the HTF be degraded and what are the effects?

Answer 10

Thermal breakdown of oil leads to hydrogen formation that permeate through the absorber and causes vacuum losses => decrease in thermal efficiency of the receiver
=> monitoring HTF degradation

Question 11

What does HTF and HSM stands for?

Answer 11

HTF: Heat Transfer Fluid aims to transfer collected heat
HSM: Heat Storage Media aims to store the collected heat

Question 12

What is the environmental footprint of CSP?

Answer 12

Low carbon footprint: 18-30g CO2 eq per kWh
Water consumption depends mainly on cooling technology => dry cooling reduces consumption but increases CAPEX and reduces efficiency

Question 13

What is a Fresnel collector?

Answer 13

The Fresnel Collector is a linear concentrating solar thermal collector

Question 14

What does PPA stands for?

Answer 14

A Power Purchase Agreement (PPA) is a legal contract between a power generator and a power purchaser, typically an electricity consumer or a utility company. Under a PPA, the power generator agrees to sell the electricity generated by a specific renewable energy project, such as a solar or wind farm, to the power purchaser at a pre-determined price for a specific period of time.

PPAs are often used to finance the development of new renewable energy projects by providing a long-term revenue stream for the project developer. This can help to attract investment and reduce the overall cost of financing the project. Additionally, PPAs can also provide a way for large electricity consumers, such as businesses or municipalities, to source a portion of their electricity from renewable energy sources, which can help to meet sustainability goals.

Question 15

What does IRENA stands for?

Answer 15

International Renewable Electricity Agency

Question 16

What does the LCOE of CSP plants say?

Answer 16

The LCOE is very high compared to other technologies, but additional value can be added if storage is integrated (grid stabilization, load shifting, …) Storage increases the investment cost but reduces the LCOE due to the higher load factor.