• Energy Research

Abstract This paper provides an overview of the costs of concentrating solar power (CSP) deployed internationally and estimates of what these costs are expected to be in Australia, both for trough and tower technologies. When an analysis is made of how to improve the efficiency of a CSP plant, there is significant potential to reduce the levelised cost of electricity (LCOE) of the plant through operation at higher temperatures. A comparison of tower and trough plants, at various operating temperatures, indicates that tower plants have a greater potential to reduce their LCOE at higher temperatures than troughs.

Floating photovoltaic (FPV) systems have generated much interest in the literature, due to the potential synergies with existing hydropower reservoirs. This is of particular relevance to Aotearoa New Zealand, where the national grid's heavy reliance on hydro resources has left the country prone to energy shortages during dry years. This paper investigates the potential implications of a 1-gigawatt peak fleet of distributed FPV systems on seven hydro schemes around the country. The results show that an FPV fleet in Aotearoa New Zealand could provide additional electricity generation when the controlled hydropower storage is low. A larger, wider rollout would allow for the reservoirs to replenish after the country's unique winter peak in electricity demand.

Abstract A CaO-based sorbent synthesized using the Pechini method is shown to have improved stability and cyclability over commercial calcium carbonates and other Ca-based sorbents for thermochemical energy storage and other chemical looping processes under N2 and a 100%–CO2 atmosphere. The improved performance is ascribed to the greater surface area and smaller grain and particle sizes of the synthesized material. A modified isoconversional approach (the Friedman method) was used to model the kinetics of the decomposition and carbonation reaction under different atmospheres. The model accounts for the dependence of the reaction rate on equilibrium pressure under different atmospheres, including a CO2 atmosphere similar to reactor conditions. For calcination, values of energy of 164 kJ mol−1 (under N2) and 307 kJ mol−1 (under CO2) were found for the calcination of Pechini-synthesized CaCO3. For the carbonation of the synthesized CaO, approximate values of 200 kJ mol−1 (25% v/v CO2) and 450 kJ mol−1 (100% CO2) were obtained for the activation energies of the chemical reaction regions. Further research into Pechini-synthesized Ca-based sorbents with supports will be carried out to further improve energy storage density and cyclic stability of sorbents.

Abstract Efficient storage of solar and wind power is one of the most challenging tasks still limiting the utilization of the prime but intermittent renewable energy sources. The direct storage of concentrated solar power in renewable fuels via thermochemical splitting of water and carbon dioxide on a redox material is a scalable approach with up to 54% solar-to-fuel conversion efficiency. Despite progress, the search for earth-abundant materials that can provide and maintain high H2 and CO production rates over long period of high-temperature cycles continues. Here, we report a strategy to unlock the use of manganese, the 12th most abundant element in the Earth's crust, for thermochemical synthesis of solar fuels, achieving superior thermochemical stability, oxygen exchange capacity, and up to seven times higher mass-specific H2 and CO yield than cerium dioxide. We observe that incorporation of a small fraction of cerium ions in the manganese (II,III) oxide crystal lattice drastically increases its oxygen ion mobility, allowing its reduction from oxide to carbide during methane partial oxidation with simultaneous Ce exsolution. High CO2 and H2O splitting rates are achieved by re-oxidation of the carbide to manganese (II) oxide with simultaneous reincorporation of the cerium ions. We demonstrate that the oxide to carbide reaction is highly reversible achieving remarkable CO2 splitting rates over 100 thermochemical cycles of methane partial oxidation and CO2 splitting, and preserving the initial oxygen exchange capacity of 0.65 molO m o l M n − 1 and 89% of the fuel production rates. Due to this extraordinarily high reversible oxygen exchange capacity, the 3% Ce-doped manganese oxide achieves an average mass-specific CO yield for CO2 splitting of 17.72 mmolCO g−1, which is significantly higher than that previously achieved in thermochemical redox cycles. More generally, these findings suggest that incorporation of small soluble amounts of cerium in earth-abundant transition metal oxides like manganese oxide is a powerful approach to enable solar thermochemical fuel synthesis.

Hydrogen demand has already significantly increased due to the industry needs. Mature technologies based on fossil fuels are not satisfactory due to greenhouse gas concerns. In response, a range of advanced processes are being developed throughout the world. Within the ‘International Energy Agency – Hydrogen Implementing Agreement – Task 25’, a multicriteria methodology was developed for the evaluation of high temperature hydrogen production processes. The aim is to guide R&D strategy by highlighting to which extent the processes may appear promising. The method that was developed is based on the elimination and choice translating the reality (ELECTRE). This study has conducted a first pass application to hydrogen production and highlights the importance of significant weightings and discriminating criteria. Decision makers can apply this method to extract their own subset of processes from the alternatives, according to their system of values defined through the selection of criteria and the associated weights.

The Aotearoa New Zealand electricity sector is undergoing a transition to more distributed electricity generation, largely driven by the private sector. Local actors, however, are increasingly interested in playing a role in the energy transition, and addressing their resilience, with community renewable energy (CRE). These projects often have a wide range of impacts, dependent on the community’s motivations, as well as the design and operation of the project. However, there is a lack of tools that can accurately quantify the impacts derived from CRE projects, and guide communities to build a portfolio of projects. This study used system dynamics modelling to analyse the impacts of CRE projects over a 40-year time span. The Energise Ōtaki community group in Aotearoa New Zealand was used as a case study given their already established CRE project and goals to expand their project portfolio. The system dynamics model showed if the community reinvested 80% of the profits from the first project into a second project would provide the greatest long-term benefit for the community in terms of the impact areas important to them. System dynamics modelling proved a useful tool in evaluating the wide range of impacts, and how they interact.

The utilisation of solar resources has become of utmost importance for the transition of the global, carbon intensive economy. In New Zealand the uptake of solar energy has increased substantially, but the relative contribution to the overall energy mix is still small. Previous research efforts on the solar resource across the country are revisited with improved satellite-modelled data from Solargis to derive a solar atlas for the country. A comparison is made with NIWA data, which shows that the modelled data are at an adequate level of accuracy and improves our understanding of the solar resource at an appropriate spatial and temporal resolution. The solar atlas makes available a commercial satellite data source and informs further investigations into how solar can, and will, play a more meaningful role in our transition to a low carbon future.