Energy availability and reliability are essential for economic growth and sustainable development. The problems with growing energy demand could be addressed by supply-side energy management. However, this task has become increasingly challenging due to high fluctuations in electricity demand and the increasing penetration of intermittent renewable energy into the electricity supply mix. This study aims to investigate the energy demand flexibility potential in the energy-intensive cement production sector. A mixed integer linear programming model (MILP) has been developed to flatten the grid's hourly demand curve by minimizing the industrial customer's hourly peak loads and maximizing the shifting of demand to off-peak periods. The result reveals that the demand flexibility potential of the case study cement plants is about 495 MWh per day, constituting approximately 28 % of the daily total electrical energy used by these cement plants, proving that the cement industry is a potential candidate for demand response strategies. By adapting the proposed model, the loads of the case study plants during the peak period of the day are reduced by an average of 75 %. In addition, case study plants have achieved an overall reduction of 188 t of CO2 emissions per day. Furthermore, the cost of consumed electrical energy for a day decreased on average by 14 % in these plants. Thus, the proposed model can help minimize the impact on grid instability and the cost of energy consumption of an industrial customer. Scenarios such as the variation of the capacity factor and onsite electrical power generation, i.e., waste heat recovery power plants, can promote the demand response strategies in the cement sub-sector. The study could be useful to energy-intensive industries and relevant policymakers to understand the demand response in maintaining power system reliability and explore ways to implement demand-side energy management strategies with appropriate electricity tariffs.

Cement production is a major consumer of energy and the largest source of industrial CO2 emissions. This study aims to perform an environmental life cycle assessment of clinker and cement production in Ethiopia, using ReCiPe impact assessment method. Inventory data (material, energy, and transportation) is collected from seven major Ethiopian cement industries. The midpoint analysis identified nine hotspot environmental concerns: global warming, ozone formation (human health and terrestrial ecosystem), particulate matter formation, terrestrial (acidification and ecotoxicity), freshwater eutrophication, human carcinogenic toxicity, and fossil resource scarcity. Human health emerged as the most significantly affected endpoint damage category by the midpoint impacts. Among the process stages included in clinker system boundary, clinker production phase (kiln emissions) is a significant contributor to the total score of the hotspot impacts, ranging from 60.7% to 91.8%. The clinker system is responsible for over 81.03% of the overall environmental burden of cement. The sensitivity analysis reveals that a 5% change in kiln energy consumption and transportation burden could lead to a reduction in hotspot impacts ranging from 1.8% to 5%. To foster reliability of this study, uncertainty analysis is also conducted. Overall, the findings indicate the need to enhance environmental sustainability in Ethiopian cement production.

More than 1.7 million ground source heat pumps are currently in operation in the European Union and a large majority of systems is using propylene glycol as secondary fluid. In this study the thermophysical properties of propylene glycol solutions with specific freezing points between −5 and −50 °C are investigated at low temperatures of interest for refrigeration and heat pump applications. The experimentally determined data are compared to a large number of data from the literature. It has been found that the freezing point results for all concentrations were in very good agreement with both Melinder (2010) and ASHRAE (2021) data. Moreover, the literature data and present study for concentrations above 40 wt-% have different density curve slopes compared to ASHRAE data. The viscosity results for concentrations below 40 wt-% were up to 21.5 % higher than ASHRAE data and the viscosity results for solutions with concentrations above 40 wt-% were lower by up to 9.7 %. The thermal conductivity results for concentrations above 40 wt-% were 10 % higher than ASHRAE (2021) data. The experimental specific heat capacity curves and other studies do not have the same linear trend as Melinder (2010) and ASHRAE (2021) data. This difference indicates that currently available ASHRAE data have been indirectly computed from thermal conductivity data or that they have not been fully experimentally validated. Finally, more studies are required to investigate concentrations below 25 wt-% to identify solutions with higher specific heat capacity than water that could be of interest for specific applications.

Refrigerants today include blends of e.g. hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFOs). HFOs have low global warming potential however are also less stable, risking compositional variations, with not much known yet. To add new knowledge, R452B (with R32, R125 and R1234yf) is analysed here, in used (7790 h in a heat pump) and pristine conditions, in a gas chromatograph with a thermal conductivity detector (TCD) and a flame ionization detector (FID). R452B was compared with moisture, N2 and a calibration blend containing CO2, R32, R125, R134a and R1234yf. The results yielded, besides the intended three components in R452B, also traces of R134a, moisture, possibly CO2 and several unknown compounds eluting before (thus lighter than) CO2. Some unknowns appeared only in TCD are thus non-combustible (including possibly O-2), while some appeared in both TCD and FID. The identification of these unknowns, calibrations for those and a comprehensive compositional analysis will follow.

In the light of global climate change and the current energy crisis, it is crucial to target sustainable energy use in all sectors. Buildings still remain one of the most energy-demanding sectors. Campus buildings and higher educational buildings are important to target due to their high and increasing energy demand. This building segment also represents a research gap, as mostly office or domestic buildings have been studied previously. In the quest for thermal comfort, a key stakeholder in building energy demand is the building occupant. It is therefore crucial to promote energy-aware behaviors. The building systems are another key factor to consider. As conventional building systems are replaced with smart building systems, the entire scenario is redrawn for how building occupants interact with the building and its systems. This study argues that behavior is evolving with the smartness of building systems. By means of a semi-systematic literature review, this study presents key findings from peer-reviewed research that deal with building occupant behavior, building systems and energy use in campus buildings. The literature review was an iterative process based on six predefined research questions. Two key results are presented: a graph of reported energy-saving potentials and a conceptual framework to evaluate building occupants impact on building energy use. Furthermore, based on the identified research gaps in the selected literature, areas for future research are proposed.

Raman-based distributed temperature sensing (DTS) is a valuable tool for field testing and validating heat transfer models in borehole heat exchanger (BHE) and ground source heat pump (GSHP) applications. However, temperature uncertainty is rarely reported in the literature. In this paper, a new calibration method was proposed for single-ended DTS configurations, along with a method to remove fictitious temperature drifts due to ambient air variations. The methods were implemented for a distributed thermal response test (DTRT) case study in an 800 m deep coaxial BHE. The results show that the calibration method and temperature drift correction are robust and give adequate results, with a temperature uncertainty increasing non-linearly from about 0.4 K near the surface to about 1.7 K at 800 m. The temperature uncertainty is dominated by the uncertainty in the calibrated parameters for depths larger than 200 m. The paper also offers insights into thermal features observed during the DTRT, including a heat flux inversion along the borehole depth and the slow temperature homogenization under circulation.

In addition to the progressive movement of countries towards the use of renewable energy sources, efficient energy consumption is another important goal set by the International Energy Agency. In heat pump technology, the use of mechanical subcooling system has a high potential for this purpose. In this experimental study, the impact of using a mechanical subcooling cycle on the performance of a heat pump system is investigated. The system is designed to supply heat at condensing temperatures of 50, 60 and 70 degrees C. Propane and isobutane are used as low GWP refrigerants in the main and secondary cycles, respectively. The results revealed that both the COP and heating capacity of the system are increased by adding the mechanical subcooling cycle up to 15.1% and 34%, respectively. To express the improvement of the system performance by means of the TEWI index, a reduction of 9-13% is calculated when the mechanical subcooling cycle is included. It is also of interest that the cooling coefficient of performance (COP2) is improved by adjoining a secondary cycle as a liquid subcooler. An optimal power ratio between the basic cycle and the secondary cycle was obtained, which is consistent with the simulation results.

Aqueous solutions of ethylene glycol are commonly used as secondary fluids in different indirect refrigeration systems and heat pumps as well as nanofluids. A very extensive literature review has been done, including more than 90 references published from 1905 to 2023. Despite the wide application and importance, especially in the energy sector, ethylene glycol solutions seem to be less investigated in low temperature ranges and more research is required to improve the quality and quantity of available data. The novelty of this paper is to investigate the most important thermophysical properties of ethylene glycol solutions in low temperatures. In this study a different approach was made and solutions having a specific freezing point temperature (between -5 and -50 ºC) rather than specific concentration were investigates in temperature ranges applicable for different cooling applications. The concentrations giving a certain freezing point temperature seemed to deviate in some cases with 1–2 wt-% between different sources. Nevertheless, the density results were in rather good agreement with all reference data. The viscosity results were lower by up to ±10% compared to reference values. Additionally, the obtained experimental results for thermal conductivity were higher by up to 12% compared to ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) data. The specific heat capacity results were higher by up to 14.6% and 5.4% than current reference data. There is a high probability that the current ASHRAE data for specific heat are actually indirectly calculated values from thermal conductivity data and not validated using differential scanning calorimetry techniques.

Global warming, caused by release of carbon dioxide from combustion of fossil fuels is forcing us to phase out these fuels and instead rely on renewable energy or nuclear power. This means that we are moving from an energy system based on fuels to one based on electricity. A large share of the energy used today is used for heating, mainly in the built environment, but also in industry. As we move towards an electricity-based energy system, there will be a very large increase in the demand for, and applications of, heat pumps. This presentation will discuss the challenges in connection to this transformation.

The cement industry is one of the most energy and emission-intensive sectors, accounting for approximately 7% of total-industrial energy use and 7% of global CO2 emissions. This study investigates the potential energy savings and CO2 abatement in the cement plants of Ethiopia. A Benchmarking and Energy Saving Tool for Cement is used to compare the energy use performance of the individual cement plants to best practices. The study reveals that all the surveyed plants are less efficient, with an average energy saving potential of 36% indicating a significant potential for energy efficiency improvement. Then, twenty-eight energy efficiency measures are identified and analyzed using a bottom-up energy conservation supply curve model. The results show that the cost-effective electrical energy and fuel-saving potentials of these measures are estimated to be 99 Gigawatt hours per year which is about 11.5% of the plants' annual electrical energy consumption and, 2.7 Petajoules per year which is to be 12.5% of the plants' annual fuel consumption, respectively. The cost-effective fuel measures have an annual average CO2 emission reduction potential of 254 kilo-tonnes per year which covers about 5% of the total CO2 emission. Sensitivity analysis is conducted using the key parameters that show some discrepancy in the base case results. This study could be used as a reference for policymakers to understand the potential for energy savings and CO2 abatement. It could also be used to design policies in improving energy efficiency in the cement sector.