Abstract

DC power distribution technology and energy storage technology can promote the safe integration of renewable energy. In this paper, a scene clustering based bi-layer energy storage optimal configuration method for AC-DC distribution system with high-penetration PVs is proposed. The upper storage capacity allocation model aims at minimizing the sum of annual investment cost and operation cost, while the lower level operation optimization model is to minimize the system annual operation cost. This paper applies the model of BESS configuration to the AC-DC distribution system, and discusses the influence of DC distribution technology, VSC control characteristics and load distribution on the BESS configuration results through several examples.

Abstract

At present, the source of hydrogen for commercial ammonia synthesis process are mainly obtained through methane reforming and coal gasification. To reduce fossil fuels consumption and CO2 emission, hydrogen production is a critical process in ammonia synthesis. Power-to-ammonia with solid-oxide electrolysis process can not only store renewable power (wind or solar), but also solve the problem of green hydrogen source. This research focuses on the techno-economic evaluation of the power-to-ammonia with solid-oxide electrolysis process. The results show that, the annual yield of ammonia is 50 kt with a purity of 99.8 mol%, with the storage capacity for renewable power being 360 GWh/year. SOEC case can achieve higher energy efficiency, the energetic efficiencies and production cost of the power-to-ammonia were 65% and 558 $/ton, respectively.
Keywords: Power

Abstract

This study presents two commercial scale processes for producing formic acid (FA) using CO2 captured from the power plant and conducts economic, energy and environmental analysis of the processes. The process is designed conceptually based on experimental data to produce high purity of FA. For the comparative analysis the FA production amount is set to 12,000 t/y. As a result of the process analysis, the process 1 considering amine shift reaction shows better results. The energy efficiency of the process 1 is 60.9%, the minimum selling price of produced FA is US$ 1,422/tFA and the CO2 emissions is 0.07 tCO2/tFA.

Abstract

Natural gas hydrates (NGHs) production has aroused wide attention in recent years. Currently, the depressurization is regarded as the most effective method for hydrate production. However, there is still exist the insufficient driving force in depressurization anaphase. In this study, two modes of depressurization combined with water-gas flow was adopted to dissociated methane hydrate (MH). The results found that the depressurization can promote hydrate dissociation at first and optimized the water-gas flow environment by increasing permeability. And the water-gas flow will provide extra dissociation driving force by accelerating heat and mass transfer and increasing chemical potential difference. What’s more, the mode of simultaneous implementation of depressurization and water-gas flow has a stronger promotion effect on hydrate production than the separate implementation of depressurization and water-gas flow.

Abstract

In order to reduce heat transmission into the interior building through roof surface to reduce building energy consumption, in the study a new hollow glass microsphere (HGMs)-based cool roof coating was developed and testified with high solar reflectivity of 95% in the solar visible wavelength. The building energy simulations based on various roof surface solar albedos were carried out extensively in five typical cities representative of five different thermal zones in China. The temperature difference and energy consumption of the prototype building were analyzed and the cooling load saving and heating load penalty in different cities were compared. Results showed that compared with substrate roof paint, the optimal HGMs-based cool roof coating improves the reflectivity by 7% and 23% in visible and near-infrared wavelength, respectively. For a naturally ventilated building, the HGMs-based roof coating could achieve over 30℃ cooler of rooftop surface and a more thermally comfortable room air temperature without extra energy supply when compared with low reflective roof. For an air-conditioning building, the office building with the proposed new coating achieves a higher annual cooling loading savings than the heating load penalties among five typical cities, consequently inducing the positive total energy savings. Kunming and Hong Kong are among the two largest energy saving rates, which indicate a stronger application potential of the HGMs-based cool roof coatings in the mild as well as hot summer and warm winter climate zones. The newly developed cool coating turns out to have good prospect for energy savings in building sectors of China.

Abstract

This paper discusses the concept of the sustainable energy ecosystem and introduces the main progress of our solid oxide electrolysis cell research. The latest progress of Power to X (P2X) technology realizes the sustainability of the multi-energy network by introducing the carbon-based cycling procedure. Among the P2X technologies, Solid oxide electrolysis cell (SOEC) is used to co-electrolyze CO2-H2O to produce synthetic gas, which is then synthesized into hydrocarbons through a fetor reactor. These two steps can effectively utilize the CO2 in the atmosphere and realize the carbon-neutral cycle. We focus on the made of Ce0.92Ni0.08O2/YSZ/LSM thin-film batteries at 600℃ for producing syngas. The experiment result shows that the observed current density reaches 0.1 mA/cm2 with a Faraday efficiency of over 95% and a hydrocarbon yield around 4 ml/min/cm2.

Abstract

This study assessed the thermo-economic performance of membrane distillation (MD) for concentrating nutrients and recover process water from digestate at a thermophilic biogas plant. The input data were derived from mapping the Uppsala Vatten och Avfall biogas system, present knowledge on anaerobic digestion process management and technologies for biogas system operating conditions in Sweden. The study evaluated the potential for recovering waste heat from the digestate effluent and boiler flue gas for use in the MD system. The thermal energy requirement, size, and separation efficiency of the MD unit were based on a previous laboratory study. The study assessed the overall energy efficiency and costs estimation of a full-scale codigestion plant with thermally integrated MD. Presented results shows that the proposed model of integrated MD system has the best thermal performance. The recovered waste heat contributed total thermal energy demand of MD and additionally it could save 19% boiler energy by heating incoming slurry. The results showed that the MD product water permeate was 3.5 L/(m2 h) at 65°C digestate inlet temperature. Specific heat demand for MD was 100 kWh/m3 with internal heat recovery. Cost estimation showed that the unit cost of MD permeate water was 3.6 €/m3 at a digestate feed temperature of 65°C. The economic assessment indicated that thermal integration of a biogas plant with MD could be economically feasible. However, long-term continuous studies are needed to determine impact of fouling and membrane lifetime.

Abstract

We evaluate the techno-economics of an integrated strategy to coproduce biofuels (Jet fuel range alkenes (JFA)) and biochemicals (pentanediols and pentane). Coproduction of biochemicals could improve the economics of biofuels production, and this study shows the feasibility of proposed strategy by stochastic analysis. Monte Carlo simulation is introduced for the stochastic analysis considering the uncertainty in major economic parameters of integrated strategy. The stochastic analysis obtains the distribution of minimum selling price of JFA. The integrated strategy considering uncertainties in key economic parameters has low minimum selling price of JFA ($2.86 and 3.17 per gallon of gasoline equivalent (GGE)), and the price is within the price range of biofuels ($2.90-4.82 per GGE).

Abstract

In recent years, due to the development of DC load and large-scale grid-connected distributed generations (DGs), the hybrid AC/DC distribution network has drawn more attentions. This paper studies the influence of voltage source converter (VSC) control strategy on hybrid AC/DC distribution network loss. Firstly, the steady-state model of VSC is established. Then, the calculation method of hybrid AC/DC distribution network loss is given based on the AC/DC distribution network power flow calculation method. Finally, the control strategy and output power of VSC are determined by genetic algorithm (GA) with the goal of loss minimization. A typical AC/DC distribution network is used to analyze the influence of the VSC control strategies to hybrid AC/DC distribution network loss. The simulation result proves the effectiveness of the proposed minimization algorithm.

Abstract

In the context of a high proportion of renewable energy and multi-energy load access to energy system, the stochastic characteristics of energy supply side and load side need to be considered. In this paper, a district integrated heat and power system (DIHPS) model including wind turbine, photovoltaic, CHP, HP and gas boiler is established. Based on the chance-constrained programming model of DIHPS, this paper studies the changes of electric power and mass flow of energy network in DIHPS under stochastic conditions, and the changes of expansion schemes when energy stations connected. The results show that considering the randomness of energy supply side and load side, the expansion cost of power lines and thermal pipelines can be effectively reduced.