Introduction
Climate Change and Anthropogenic Causes of Warming
Its effects, along with those of other anthropogenic drivers, have been traced throughout the climate system and are most likely the dominant cause of the observed warming since the mid-20th century." 6. The warming caused by anthropogenic emissions of greenhouse gases (GHGs) is already impacting many different natural phenomena, with more severe impacts expected as warming continues. 6 These impacts include increased frequency and intensity of droughts, heat waves and precipitation events such as hurricanes. 8 Excess carbon absorption by the oceans causes acidification of the sea, which threatens many species and ecosystems, as well as marine industries such as fishing. 8 The Greenland and Antarctic ice sheets are losing mass at an accelerated rate, Arctic sea ice extent is shrinking, permafrost is warming and sea levels are rising.9 All these phenomena have negative implications for human-serving systems such as food, water, energy, tourism and trade.9 While many of these effects of climate change are already occurring and therefore impossible to completely avoid, they are still possible to mitigate their progress if we act quickly.8.
Net-Zero Emissions
- Emissions by Sector
- Load-Following Electricity
- Transportation and Fuels
While this transformation will present challenges across all sectors, certain areas are particularly difficult to decarbonize given current technological and economic constraints.14 An overview of such "hard-to-eliminate" emissions by used data from 2014 is given in Figure 1.4. Emissions from electricity generation account for the largest share of global greenhouse gas emissions of any single economic sector.6 There is a consensus among many studies of electricity generation that variable renewable energy (REE) sources such as solar and Wind can decarbonize a large part of the electricity sector, but moving beyond a generation mix of ~80% renewables to achieve full decarbonization becomes much more difficult.14–16 The inherent variability of solar power and wind due to weather patterns makes it difficult to ensure that there is always enough production to meet electricity demand.15,17 This variability persists over a range of timescales, requiring strategies to deal with the changes. per hour, day-night cycling, seasonal variations and inter-annual variability. 17.
Solar Fuels Devices
Photons with energy less than the band gap are transmitted through the semiconductor instead of being absorbed. The potential of the conduction band edge at the semiconductor-liquid junction must be more negative than the proton reduction potential of the HER.
Scope of Thesis
In Figure 4.4 (b), dispatch from natural gas was limited to meeting no more than a given percentage of demand, requiring VRE generation to cover the rest of demand. In Figure 4.7 (a), the cost of CSP + TES was varied as a single unit by simultaneously applying the same cost multiplier to each technology, and similarly the cost of PV+battery was also varied as a unit.
Corrosion Pathways in Silicon Microwire Solar Fuels Devices
Introduction
Free-standing microwire arrays should also exhibit improved corrosion resistance, provided that pitting corrosion due to a defect in the protective coating of a light absorber cannot physically propagate to microwires that are not in electrical contact with the unprotected, corroded material. Although Si passivates as a photoanode under illumination in most aqueous electrolytes due to oxide formation at pinhole defects in protective coatings, we evaluated the stability and failure modes of such systems in alkaline electrolytes in the dark to obtain conditions under which Si actively etches.
Experimental Methods
Average hourly charging and discharging behavior for TES in each month of the year in the base case system. Average hourly charging and discharging behavior for batteries in each month of the year in the base case system.
Results and Discussion
Conclusions
Fabrication of III-V Nanowires for Light Absorption
Introduction and Motivation
Photoelectrochemical devices offer one way to produce green hydrogen as an emission-free fuel.35,36 In order to compete with low-cost solar PV devices and electrolyzers, they must achieve high efficiencies of solar energy into hydrogen.35,63,64 In pursuit of this, the goal has been proposed that tandem devices combining a wide and narrow bandgap absorber capture a wider range of the solar spectrum.41,65 Modeling of such devices shows that they are capable of achieving nearly 30% solar-to-hydrogen efficiency, as shown in Figure 3.1. However, even greater efficiency is possible by exploiting the nanometer scale optical properties in direct bandgap III-V semiconductors. Here, we report fabrication methods to create nanostructured GaAs and InP that can be tailored to realize the above advantages in future devices.
GaAs Nanostructure Fabrication Methods
SiCl4 acted as a chemical etchant, forming partially chlorinated GaClx and AsClx (x = 1-3).69 Ar increased the etching anisotropy by physical sputtering and CH4. In order to achieve the optimal structures shown in Figure 3.2, higher aspect ratio wires are still required. Using thicker mask layers, longer etch times, and increasing the etch anisotropy by increasing the Ar flow can help to obtain improved structures.
InP Nanostructure Fabrication Methods
Future Work
When TES was a storage option, CSP with TES was always present in the cheapest systems to add flexibility to the system. Reducing the cost of CSP and TES would also not eliminate the need for long-term storage like PGP. Both storage technologies were used less without PGP than with PGP in the cheapest systems.
The Role of Concentrated Solar Power in Energy Systems
Introduction
The first commercial CSP plant was built in the USA in the 1980s, and CSP has been in continuous use since then.27 However, global CSP capacity grew slowly during this period, with development taking place only in a select few countries.27 CSP and TES currently enjoy renewed interest, especially among solar belt countries in Africa80,81 and the Middle East,27 as well as in China, which is the world leader in planned new CSP capacity.27 Concentrated solar energy offers several potential advantages for VRE-based electrical systems. The impacts of CSP with TES on the power grid have been investigated in a number of studies in different geographic areas.80,90–95 One study on the Brazilian power system found that adding CSP with TES was a cost-effective way to add marginal dispatchable capacity that complemented wind. and PV generation.90 CSP+TES also added flexibility to the grid, especially in winter when Brazil's large hydrologic resources were less available.90 Another study similarly found that CSP improved flexibility in the Chilean power system, with low-cost scenarios that lead to CSP, with TES accounting for about one-third of energy dispatched by 2037.91 In the US, a Western Interconnect study comparing CSP+TES with renewable generators without other storage technologies found that CSP+TES can reduce the need for expensive start-up and operation of peaking fossil fuel power plants at high speed.96. The ability to explore a wide range of scenarios is important because of the uncertainty in cost projections for current renewable energy generation technologies as well as in the development of future technologies.
Methods
- Model Formulation, Costs, and Assumptions
- Solar and Wind Data
- Demand Data
Values/kg for H2 storage and electrolysis plant were converted to kWh for model inputs using a lower heating value (LHV) of 33.33 kWh/kg for hydrogen. Wind performance factors were calculated for a GE 1.6–100 turbine with a nameplate capacity of 1.6 MW using the methods described in Ref. The mean absolute percentage error (MAPE) across all balancing authorities was calculated to be 3.5% with a relatively small bias of 0.33%.116 The base year used for the demand data was 2017.
Results
- Increased Grid Flexibility through CSP+TES
- Grid Flexibility from other Sources
- Technology Combinations and Interactions
- Cost Drivers for CSP+TES Penetration in the Grid
CSP+TES was not built until natural gas was limited to meet more than. More CSP+TES were built into systems without PGP long-term storage, as seen when comparing the base case with the TES+Battery case in Figure 4.5 (a) and Figure 4.5 (b). However, in the absence of PGP, adding CSP+TES to the PV+battery system reduced system costs by 2¢/kWh.
Discussion
- CSP with TES as a Storage Technology
- CSP with TES in a System without Long-Duration Storage
- Considerations for CSP and TES Integration into Renewable Systems
- Impact of Firm Generators
- Limitations
Even significant cost reductions for solar towers will only maintain CSP+TES' role as a short-term storage technology in these idealized VRE-dominated 100% reliable, least-cost-dominated electricity systems. The impact of adding such firm generators was evaluated by allowing either natural gas with CCS (Figure A.11) or nuclear power (Figure A.15) to be included in the modeled least-cost electricity systems. For systems with natural gas with CCS, CSP+TES was only present in the idealized lowest cost system if natural gas with CCS was limited to ≤3% of total dispatch.
Conclusions
The addition of CSP with TES was found to lower costs significantly only when long-term storage was not included in the system. Without long-term storage in the system, batteries and TES maintained mutually similar temporal charging patterns. Modeling Concentrated Solar Power (CSP) in the Brazilian Energy System: A Soft-Linked Model Coupling Approach.
Summary and Future Outlook
Summary
The substrate-supported microwires were subject to top-down corrosion due to defects in the TiO2 cap layer, with propagation through the substrate resulting in secondary bottom-up corrosion processes. The free-standing microwires in the membranes showed uniform corrosion from the bottom up through the membrane, consuming the entire sample over the 10-day period studied. However, low-cost storage from TES has been found to improve grid flexibility and reduce the amount of unsatisfied demand in the system.
Micro- and Nano-Wire Solar Fuels Devices
Systems Modeling for Multi-Benefit Technologies
It is also important to consider factors beyond purely techno-economic concerns that will influence decision-making in the net zero transition. Several examples of this type of integration already exist,129 and I hope they will become more common as the field develops.
Future Outlook
Model Formulation
- Nomenclature
- Cost Calculations
- Constraints
- Power-to-Gas-to-Power Implementation
- Thermal Energy Storage Implementation
- Objective Function
- Data and Code Availability
The rate of charge and discharge for hydrogen storage is limited by the electrolyser and the fuel cell. The charge and discharge rate for TES is limited by the capacity of the solar array and the CSP turbine as shown below, where 𝑠′′ denotes the thermal energy storage, 𝑔′ denotes the capacity of the solar array and 𝜈′′.
Technology Cost Calculations
- Generation Technologies
- Power-to-Gas-to-Power
The power used to compress the hydrogen gas was included in the net electrolysis efficiency, and no ramp rate limitation was used. This separation is important because the stack has an estimated life of 7 years compared to 40 years for BoP components. The electrolysis facility used in the model consists of this combined electrolyzer, BoP and compressor.
Supplementary Figures and Tables
Although the capacity values fluctuated in different years, they all include CSP+TES in the optimal system, indicating that the role of CSP+TES exists over multi-year time frames. Here, batteries are used to a large extent in the summer and winter months to compensate for low wind and solar resources respectively, with smaller peaks in the intervening months. Greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development and efforts to eradicate poverty;.
Solar for Industrial Process Heat: A Review of Technologies, Analytical Approaches, and Potential Applications in the United States. Temporal and spatial variability of wind resources in the United States as inferred from a reanalysis of the Climate Prediction System.
