Abstract

Biomass can be used as an alternative fuel in micro gas turbines to produce electricity, heat and/ or cooling. This is an affordable carbon-neutral renewable energy source which is widely available in most African countries. In this project the main aim is to gather information and data to evaluate the feasibility and the market potential of this technology in three sub-Saharan African countries. This includes data about the energy market, information on feedstock availability in different regions, statistics on the electricity grid, the demand profiles of different consumers, as well as insight on the national policies and regulation. The information is used to help understand the needs of the energy market in the partner countries and the potential of the proposed technology.

Abstract

This work presents a multi-stage stochastic Mixed Integer Linear Program with binary recourse for optimizing the day-ahead unit commitment of power plants and virtual power plants operating in the day ahead and balancing markets. Scenarios are characterized by profiles representing the expected maximum quantities of energy/bids accepted by the balancing market, and photovoltaic panels generation for each hour of the day. Since the deterministic equivalent MILP model cannot be solved in a practical computation time (> 24 hours), a novel decomposition is developed. Results show how the proposed decomposition approach provides close-to-optimal solutions in much shorter computational time (<20 minutes).

Abstract

The dispatchability of renewable power plants and the role of energy storage are gaining relevance and hybrid technologies, such as CSP-PV plants, constitute a promising solution that can effectively exploit different synergies, lowering the production costs and, at the same time, increasing the overall system dispatchability.
This work proposes a model aimed at optimizing the design and operation of highly integrated concentrated-solar – photovoltaic power plants. The integration level occurs not only via the energy management system but also through the introduction of electric heaters in the TES, physically linking the CSP and PV plants.
The entire system has been optimized developing an accurate Mixed Integer Linear Programming model. It was demonstrated, how compared to the respective separate configurations, hybrid solutions can achieve similar performances at a lower LCOE.

Abstract

CO2 storage in the reservoir is the most common method to mitigate global warming. In this work, the influence of sand particle size on the CO2 hydrate formation kinetics has been investigated in a pilot-scale reactor (25 L) at three different sand particle sizes (300-500 µm, 500-710 µm, and 710-1000 µm). The experiments are carried out at 275.15 K temperature and initial pressure of 3.5 MPa. The parameter studied in the present work are induction time, amount of gas consumption during hydrate formation, water to hydrate conversion, and hydrate saturation. It is observed that the induction time is lowest for the smaller sand particle size. Gas consumption, water to hydrate conversion, and hydrate saturation are higher for smaller sand particle sizes. The results show that smaller sand particle size enhances the hydrate formation kinetics. The present study can be helpful in selecting a suitable reservoir for CO2 sequestration via hydrate formation.

Abstract

The increase of Renewable Energy Sources (RES) has given momentum to demand-side flexibility, led by Demand Response (DR), to counteract the uncertainties of the new electricity system. Meanwhile, consumers, with the help of Demand Aggregators (DA), are becoming active participants by engaging in flexibility actions. As a tool for the experimental assessment of DR, this work integrates a microgrid laboratory with an aggregation platform. To test the environment created and analyse the impact of DR, two consumers have been defined using virtual, emulated and real elements: a residential user with a Heating Ventilation and Air Conditioning (HVAC) unit and a prosumer equipped with Photovoltaic (PV) panels and a second-life battery.

Abstract

Selective Catalytic Reduction (SCR) is a technique based on urea-water solution (uws) to reduce nitrogen oxides (NOx) emitted from diesel engines. In this work, experimental investigation on injection of water and uws spray interaction with a hot mixer plate in exhaust gas test bench is presented. The work was performed with a commercial six-hole pressure-driven injector dosing into a flow channel emulating typical diesel exhaust flow conditions. Kinetic properties of the droplets were studied using Phase Doppler Anemometry (PDA) measuring the droplet sizes and velocities prior to the wall impingement. Based on these, characterization of the influence of gas velocity, fluid flow rate and change of spray fluid from water to uws was deduced. A decrease in the spray cooling effect was observed when the gas velocity was increased due to increased interaction of the droplets with the gas flow before impingement. An increase in the gas velocity results in higher wall temperatures and a higher spray mass flow shifts the spray/wall interaction regime towards deposition for smaller droplets. The breakup regimes are seen to shift from rebound and thermal breakup to deposition and splash on reaching a steady state wall temperature.

Abstract

Carbon pricing policy is one of the most efficient tools to mitigate carbon emissions. However, additional carbon cost alters the production behavior and sectoral development, thus leading to income redistribution and regional disparity. Revenue recycling schemes use the carbon pricing revenue to reduce preexisting revenue-motivated taxes. This paper intends to evaluate the effect on income inequality and regional disparity of carbon pricing policy with different revenue recycling schemes. This study adopts the China Hybrid Energy and Economic Research (CHEER) model, a dynamic CGE model, and extends it to the CHEER-Plato model in order to better study the effects of the carbon pricing policy and the revenue recycling schemes. Results show several key findings. First, carbon pricing policy without recycling the revenue will lead to greater income inequality, increasing the national Theil index by 0.87% and 3.61% in 2030 and 2040 respectively. The inter-provincial disparity will raise obviously by 3.97% and 12.72%, while the inner-provincial inequality will change slightly. Second, recycling carbon pricing revenue through individual income tax return reduces income inequality. Compared with policy without recycling schemes, returning the revenue with progressive tax return rates by labor income groups, reduces the Theil index by 2.53% and 7.88% in 2030 and 2040, while the scheme with region-specified return rate by 1.42% and 4.42%, and the scheme with uniform return rate by only 0.43% and 1.23%. Third, carbon pricing policy reduces the inequality in Shanxi and Inner Mongolia by more than 2% and revenue recycling scheme with progressive tax return rates by labor income groups further narrows the income gap in Yunnan, Guizhou, and Xinjiang by over 3% in 2030.

Abstract

A multi-energy thermochemical hybrid heat and power (CHP) system with two-stage storage is presented and analyzed in this study. The proposed system includes parabolic trough solar collectors, a thermochemical reactor, an internal combustion engine (ICE) and a two-stage storage of thermal energy and chemical energy, which uses solar energy and methanol as input and outputs power and thermal energy. With the two-stage storage, solar energy and exhaust heat are stored as thermal energy in the first stage and further converted into chemical energy in the second stage, which is stored in the syngas tank. Due to the two-stage energy storage, the heat-to-power ratio (HPR) of the proposed system can be adjusted and controlled between 0.67 and 2.02 under rated working conditions. The load match between energy supplier and receiver is improved, reducing additional energy input and energy waste. Compared to the reference CHP system, the fuel saving ratio (FSR) of the proposed system is further improved from 34% to 52% under the design conditions. The methanol decomposition driven by the combination of solar energy and exhaust heat increases the power generation efficiency for methanol fuel. The fuel source conversion reduces the irreversible loss of fuel combustion. Solar thermal energy is upgraded into syngas chemical energy. A high net solar-to-electric efficiency (22.85%) is achieved at a low heat-collecting temperature (538.15 K). This study provides a promising approach for the active regulation of solar-fuel hybrid distributed systems.

Abstract

Hydrogen starvation is an essential limiting factor of lifetime for commercial polymer electrolyte membrane fuel cell (PEM fuel cell) stack. In this paper, a segmented single 25 cm2 PEM fuel cell is utilized to investigate hydrogen starvation phenomenon. The current distribution under different hydrogen stoichiometry conditions is characterized based on contour maps, and the voltage drop phenomenon is tracked constantly during the whole duration until the cell reversal occurs. The results approve that voltage drop becomes more rapid and more severe with the decreasing number of hydrogen stoichiometry. Furthermore, hazardous carbon support oxidation induced by hydrogen starvation causes current density redistribution in the voltage drop process, reflecting irreversible performance degradation and component deterioration of PEM fuel cell.

Abstract

Cogenerative geothermal power plants can supply thermal energy required by energy-intensive activities, such as greenhouses heating. The required thermal load in these systems usually follows the daily temperature trend, leading to not negligible load fluctuations on the power plant side that need to be managed, in case a constant electric output from the plant is required (e.g. because the energy has been already sold on the day-head electric energy market). The supplied heat flow rate must be constant to avoid a fluctuating operation of the cogeneration system. This paper investigates the opportunity of using a thermal storage to manage this load fluctuations and keep the system stable. Results show that even an oversized storage tank may not be sufficient to reach the desired set point conditions, especially if the load forecasting is incorrect. For this reason, it is necessary to increase the supplied heat flow rate to reduce energy shortages and use a cooler to dissipate energy surpluses. Results show that it is possible to achieve setpoint conditions by increasing the supplied heat flow rate by 20% and using a cooler do dissipate thermal energy surplus. This performance worsens when the load forecast is not accurate, though shortening the period with a fixed heat flow rate can be beneficial.