The cross-cutting issues that have been identified above are summarised in the following Table. By the specific parameters, it identifies targets and action items where applicable. TABLE I: Research Priorities for Cross-cutting Issues Topics
Objectives
Light reflective surfaces
• Identify and develop lightParameter: Durability weight and durable reflective Demonstrate the durability of aluminum, surfaces with high reflectance thin glass mirrors and polymer films
Glass reflectors with anti-soiling coating
• Reduce maintenance cost and plant water consumption => enhance commercial deployment of STE plants in desert areas with high solar radiation levels
Parameter: Water requirement for mirror washing [m3/m2/y] Target: < 0.015 (water consumption = - 50% in southern Spain) LCOE = - 0.1%
Mirror glass with higher solar transmissivity
• Increase the reflectance of glass solar reflectors and the efficiency of the receiver tubes
Parameter: Glass solar transmittance (ρ) Target: ρ = 0.93 for glass thickness = 3.5mm LCOE = - 1% for CR LCOE = - 2% PT & LF
Receivers
Selective coatings with better optical properties
• Increase solar-to-thermal efficiency - of the receiver tubes used in PT and CLFR systems - of the tubular receivers in CR systems
Parameter 1: Solar emittance (ε) Parameter 2: Solar absorbance (α) PT and LF: Target 1: ε < 0.1 (450°C) Target 2: α ≥ 0.96 (vacuum conditions) LCOE = -1.5% CR: Target 1: ε < 0.25 (600°C) Target 2: α ≥ 0.94 (stable atmospheric conditions) LCOE= - 2%
X
Heat transfer fluids
Synthetic oil with new chemical formulation
• Lower the value of viscosity at low temperature • Add PCM • Consider binary systems
Parameter: O&M solar field cost Target: 5 to 10% reduction
X
Low meltingtemperature salt mixtures
• Reduce the thermal losses overnight and the risk for crystallisation in the piping of STE plants using molten salt => reduce maintenance costs
Parameter 1: Melting temperature (T) and thermal stability limit of the novel salt mixture Parameter 2: Overall efficiency η Parameter 3: Cost (C)
Parameter/Target/Action
Short
Mid
Long
X
X
X
X
Strategic Research Agenda
Mirrors
X
Target 1: T ≤ 100°C (good thermal stability up to 450°C) Target 2: η = + 4% (15.2% > 15.8%) Target 3: C < 40% of the cost of oil LCOE = - 4%
X
Target 1: T ≤ 100°C (good thermal stability T > = 600°C) Target 2: η = + 6% (15.2% > 16.1%) Target 3: C < 120% of the cost of the Na/K 60/40 wt% nitrates mixture LCOE = - 5.5% Action: Implementation of a small plant (< 5 MWe) to investigate O&M related issues using new working fluid under real solar working conditions Pressurised gas
• Increase solar-to-electric efficiency
• Develop novel design Development absorber tubes, with of high suitable metals and thickness pressure to withstand pressure and absorber tubes temperature limits for DSG Storage
Advanced high temperature thermal storage systems
Control and operation tool
7
Parameter: overall conversion efficiency Parameter: Working pressure (p) and temperature (T) of the absorber tubes Target 1: p = 125 bar at T = 575°C for PT and LF Target 2: p = 150 bar at T = 700°C for CR
X
• Develop new systems based on new materials or new concepts in order to obtain technical and economically feasible solutions at temperatures above 600°C
Parameter: Storage working temperature (T)
Target 2: Storage concepts for air receivers with T > 1,000°C by 2020
X
• Develop faster & cheaper tools & procedures => maximise solar radiation => improve efficiency and LCOE
Parameter: Cost and time required to assess the optical quality of a life-size solar concentrator Target: < 2 kW, < 6 h, total uncertainty < 1.5% (11.2 x 5.7 m PT module, a 120 m2 heliostat, or any concentrator with an aperture area ≥ 30 m2) Action: Implementation and evaluation of a prototype for the intended on-site evaluation equipment
X
Target 1: T = 600°C Storage concepts for air receivers with T = 800°C by 2015
X
december 2012
65