Annual Energy Cost Research Articles

Investigation of enhancement in the thermal response of phase change materials through nano powders

A major problem faced by Phase Change Materials (PCM) based latent heat thermal energy storage systems is the slow thermal response. In this study, the feasibility of nano phase change materials composites is investigated experimentally by using various types of nanoparticles in PCM, to improve thermal response by increasing the thermal conductivity. Heat transfer enhancement of PCM composites (RT26 and coconut oil) is achieved by acquiring better thermophysical properties through seeding nanoparticles in PCM. RT26 and coconut oil are beneficial due to the absence of corrosion to metallic containers. A thermal response investigation is conducted with a flat slab type latent heat thermal energy storage unit. It was observed that the increase in thermal conductivity of PCM by seeding nanoparticles is useful for the improvement of heat transfer. Carbon nanotubes have shown better performance as compared to Al2O3 and Fe3O4 nanoparticles. It was further analyzed that at a 1 wt percent concentration of nanoparticles, the maximum heat transfer enhancement in RT26 caused by Fe3O4, Al2O3 and carbon nanotubes nanocomposites is up to 20.01, 36.68 and 64.21% respectively. The maximum heat transfer enhancement in coconut oil caused by Fe3O4, Al2O3 and carbon nanotubes nanocomposites is up to 8.83, 14.84 and 33.38% respectively. Therefore, it is revealed that RT26 has more potential for heat transfer enhancement as compared to coconut oil. This is due to the percentage improvement in the thermophysical response of RT26 as compared to coconut oil. The economic and environmental analysis was conducted to compare the performance of latent heat thermal energy storage unit with and without the application of nanoparticles in PCM, to estimate the most viable candidate among various nano composites. The economic analysis presented the lowest annual energy running cost and Net Present Value(NPV) for nanocomposite of carbon nanotubes in RT26 is Rs.-4381 and RS.-36375 respectively. Whereas the maximum annual energy cost and NPV for pure RT26 are Rs.-12240 and Rs. -75548 respectively. The NPV for Fe3O4 and Al2O3 is Rs.-62207 and Rs.-53062 respectively. The cost and NPV were Rs.-6646 and Rs.-55226 in the case of carbon nanotubes in coconut oil. It shows that the trend is the same in the case of Fe3O4 and Al2O3 nanoparticles in both RT26 and coconut oil, unlike of carbon nanotubes. The environmental analysis shows that the maximum and minimum payments of carbon dioxide by carbon nanotubes and Fe3O4 nano composites respectively in RT26, are Rs.7000 and Rs.2176. While the corresponding values are Rs.2975 and Rs.798 in the case of coconut oil. Hence, carbon nanotubes in RT26 have the highest economic and environmental viability. Accordingly, the enhancement in heat transfer using these nanoparticles will be helpful in air conditioning applications like animal houses.

Cool Roofs in the US: The Impact of Roof Reflectivity, Insulation and Attachment Method on Annual Energy Cost

While it is well-known that cool roofs can efficiently reduce cooling demand in buildings, their overall energy performance in mixed and cold climates has been a topic of debate. This paper presents a comprehensive simulation study to evaluate the combined impact of roof reflectivity, insulation level, and construction type (adhered vs attached) on annual energy demand and energy costs in the United States, for different buildings and climate zones. EnergyPlus was used to model three building types (retail, office, and school buildings) for the 16 most climate-representative locations in the US using typical reflectivity and insulation values. The results show that (i) roof reflectivity is equally important to roof insulation in warm climates; (ii) for low-rise offices and schools, the benefits of reflective roofs vs dark-colored roofs are clear for all US climatic zones, with higher savings in warm climates; (iii) for big-box-retail buildings, reflective roofs perform better except for cold climate zones 7–8; (iv) dark-colored, mechanically attached roofs achieve slightly better performance than reflective roofs in mixed and cold climates. Decision makers should consider building type, climatic conditions, roof insulation levels, and durability performance, along with roof reflectivity, when assessing the overall potential benefits of cool roofs.

Greening Existing Buildings in Brunei Darussalam

Building is the largest consumer of resources and the biggest polluter of the environment, including energy consumption and greenhouse gas emission. Greening existing buildings, an extension of green building concept to existing buildings, can potentially help to improve such issues. Greening process can considerably reduce energy consumption in buildings and thereby reduce the carbon dioxide emission. On the basis of a recent study on energy consumption in residential buildings in Brunei Darussalam, this paper demonstrates the potential savings in energy consumption and reduction of energy cost, if modern and energy-efficient electrical appliances are used in place of the existing conventional features/appliances. The result sshow that an average household can potentially reduce its yearly energy consumption by 32.74% and they can save annual energy cost of up to 52.20%. It is also seen that the appliances with higher energy consumption, like air conditioners and refrigerators, can offer higher savings of both energy consumption and energy cost, with relatively smaller extra initial replacement costs. A favourable awareness programme by appropriate authority is likely to motivate people to use such practices and help to reduce energy consumption and emission of greenhouse gases.

Nationwide assessment of energy costs and policies to limit airborne infection risks in U.S. schools

Practices such as improved ventilation and air filtration are being considered by schools to reduce the transmission of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) that causes the pandemic of coronavirus disease 2019 (COVID-19). Improved ventilation may significantly increase the energy cost of heating, ventilation, and air conditioning (HVAC), exacerbating financial challenges schools face amidst the worst pandemic in decades. This study evaluated HVAC energy costs for reducing COVID-19 airborne infection risks in 111,485 public and private schools in the U.S. to support decision-makings. The average annual HVAC energy cost to maintain the infection risk below 1% for the schools in the U.S. is estimated at $20.1 per square meter or $308.4 per capita with improved ventilation and air filtration, where the private schools have higher costs than the public schools on average. The cost could be reduced by adopting partial online learning. It was also found that additional cost to control infection risk with increased ventilation and air filtration is significantly lower for PK-5 schools than that for middle and high schools, indicating the possibility of remaining in-person instructions for PK-5 schools with necessary governmental assistance. Analyses of school HVAC energy costs to reduce airborne infection risks under different intervention scenarios provide important operational guidelines, financial implications, and policy insights for schools, community stakeholders, and policymakers to keep schools safe during the ongoing pandemic and improve preparedness for epidemics projected in the future.

The implications of ambitious decarbonisation of heat and road transport for Britain’s net zero carbon energy systems

Decarbonisation of heating and road transport are regarded as necessary but very challenging steps on the pathway to net zero carbon emissions. Assessing the most efficient routes to decarbonise these sectors requires an integrated view of energy and road transport systems. Here we describe how a national gas and electricity transmission network model was extended to represent multiple local energy systems and coupled with a national energy demand and road transport model. The integrated models were applied to assess a range of technologies and policies for heating and transport where the UK’s 2050 net zero carbon emissions target is met. Overall, annual primary energy use is projected to reduce by between 25% and 50% by 2050 compared to 2015, due to ambitious efficiency improvements within homes and vehicles. However, both annual and peak electricity demands in 2050 are more than double compared with 2015. Managed electric vehicle charging could save 14TWh/year in gas-fired power generation at peak times, and associated emissions, whilst vehicle-to-grid services could provide 10GW of electricity supply during peak hours. Together, managed vehicle charging, and vehicle-to-grid supplies could result in a 16% reduction in total annual energy costs. The provision of fast public charging facilities could reduce peak electricity demand by 17GW and save an estimated £650 million annually. Although using hydrogen for heating and transport spreads the hydrogen network costs between homeowners and motorists, it is still estimated to be more costly overall compared to an all-electric scenario. Bio-energy electricity generation plants with carbon capture and storage are required to drive overall energy system emissions to net zero, utilisation of which is lowest when heating is electrified, and road transport consists of a mix of electric and hydrogen fuel-cell vehicles. The analysis demonstrates the need for an integrated systems approach to energy and transport policies and for coordination between national and local governments.

Transformation towards a carbon-neutral residential community with hydrogen economy and advanced energy management strategies

Cleaner power production, distributed renewable generation, building-vehicle integration, hydrogen storage and associated infrastructures are promising for transformation towards a carbon–neutral community, whereas the academia provides limited information through integrated solutions, like intermittent renewable integration, hydrogen sharing network, smart operation on electrolyzer and fuel cell, seasonal hydrogen storage and advanced heat recovery. This study proposes a hybrid electricity-hydrogen sharing system in California, United States, with synergistic electric, thermal and hydrogen interactions, including low-rise houses, rooftop photovoltaic panels, hydrogen vehicles, a hydrogen station, micro and utility power grid and hydrogen pipelines. Advanced energy management strategies were proposed to enhance energy flexibility and grid stability. Besides, simulation-based optimizations on smart power flows of vehicle-to-grid interaction and electrolyzer are conducted for further seasonal grid stability and annual cost saving. The obtained results indicate that, the green renewable-to-hydrogen can effectively reduce reliance on pipelines delivered hydrogen, and the hydrogen station is effective to address security concerns of high-pressure hydrogen and improve participators’ acceptance. Microgrid peer-to-peer sharing can improve hydrogen system efficiency under idling modes. Furthermore, the integrated system can reduce the annual net hydrogen consumption in transportation from 127.0 to 1.2 kg/vehicle. The smart operation (minimum input power of electrolyzer and fuel cell at 65 and 80 kW) can reduce the maximum mean hourly grid power to 78.2 kW by 24.2% and the annual energy cost to 1228.5 $/household by 38.9%. The proposed district hydrogen-based community framework can provide cutting-edge techno-economic guidelines for carbon-neutral transition with district peer-to-peer energy sharing, zero-energy buildings, hydrogen-based transportations together with smart strategies for high energy flexibility.

Combined heat and power system based on Solid Oxide Fuel Cells for low energy commercial buildings in Qatar

Commercial buildings in Qatar account for 19% of the total energy consumption in the country. To reduce this significant amount of energy, a Solid Oxide Fuel Cell Combined Heat and Power (SOFC CHP) system with natural gas as fuel is studied. An office building model is created in eQuest energy modeling package. Several baseline cases were considered to optimize the HVAC system and loading profile to utilize the SOFC to its full extent. These baselines are: electric chiller, absorption chiller, and combined electric-absorption chiller systems. Performance curves were analyzed for a range of SOFC CHP system capacities (25–250 kW) in terms of energy produced, utilized thermal energy, overall efficiency and annual energy costs to assess potential cost savings. Results showed that using SOFC CHP with combined electric-absorption chiller system can reduce the annual energy cost by 67% compared to the baseline case with electric chiller. Moreover, optimum overall efficiency of the system can reach 73%. Finally, an environmental impact assessment was evaluated in terms of CO2, NOx, and SO2 emissions. It was found that application of SOFC CHP system resulted in reductions in CO2 emissions of 30%, NOx of 90%, and SO2 of 90%.

Технико-экономическое обоснование стоимости транспортировки сточных вод для ирригационных целей в административном округе Кербела (Ирак)

Introduction. The study presents an assessment of the economic feasibility of different pipe materials used to transport treated wastewater. The choice was made between pipes made of ductile iron, glass-fiber reinforced polyester (GRP), concrete, and plastic. Hydraulic calculations of operation of an irrigation water supply and distribution system were made using WaterCAD V8i software. Two options of the system operation, that entail different flow rates and diameters, are considered: if the flow rate is equal to 1.16 m3/s and pipe diameters vary from 800 mm to 1,200 mm, and if the flow rate is equal to 4.63 m3/s, and pipe diameters vary from 1,600 to 2,000 mm. Materials and methods. The article analyzes the legal and regulatory documentation on design and construction, urban planning solutions for residential areas, architectural and structural solutions for apartment buildings, statistical and analytical reports on housing construction in Russia, presented on the Internet. Results. Irrigation water represents treated wastewater fed by the wastewater treatment facilities in the city of Karbala, Iraq. Two hydraulic models were designed with account for the above-mentioned costs. Head losses were estimated for each model with regard for all studied materials and pipe diameters using the WaterCAD V8i software and a mathematical model for the purpose of selecting the optimal pipe diameter. Conclusions. A mathematical model was developed to calculate the cost of transporting wastewater in pipes having different diameters and made of four different materials. The ratio of costs to the diameter of pipes, made of four different materials, was identified by developing an empirical equation. The co-authors used the Darcy – Weisbach technique and the Hazen – Williams method to calculate the operating costs with regard for variable diameters, flow rates for the two models, head losses due to friction, annual operation time, annual cost of electric energy, and the energy efficiency of the unit. Thus, a mathematical model was obtained, that can be applied to select the most optimal pipe diameter.

Architectural Sustainability on the Impacts of Different Air-Conditioning Operational Profiles and Temperature Setpoints on Energy Consumption: Comparison between Mosques with and Without HVLS Fan in the City Center Mosques

The use of air-conditioning (AC) in conjunction with high-volume, low-speed (HVLS) fan has become a trend in retrofitted mosque buildings in Malaysia to improve thermal comfort conditions. However, the energy impact of operating AC and HVLS fan simultaneously is unknown. This study compares the annual energy consumptions between mosques with and without HVLS fan installed and investigates the optimum temperature setpoints and operational profile to improve the mosques' energy efficiency. The comparison using the Building Energy Index (BEI) did not clearly show the superiority between the two groups in terms of energy performance. The study found that both studied mosques could produce around 1-4.9% energy reduction when the AC temperature setpoint was increased by 1˚C and could result in the highest cost-saving of about 4.9% when the temperature was set at 27˚C. A 30-minute AC operation during each daily prayer, except Subuh, could save between 14.8-16.7% annual energy consumption and about 15.15-16.6% annual energy cost. The paper concludes that the selection of 24-27˚C temperature setpoints with a 30-minute AC operational profile during prayers time with consideration Friday prayers and Ramadhan activities produced 18.4-20.6% savings in energy cost. This study calls for reevaluations of AC temperature setpoints configuration standards and operational characteristics in mosque buildings to reduce the buildings' energy consumption. This paper contributes to the development of future energy standards for mosque designs and operations in Malaysia.

The cost of grid stability with 100 % clean, renewable energy for all purposes when countries are isolated versus interconnected

This study examines the impacts on energy costs and requirements of interconnecting versus isolating the electric grids of countries in Western Europe when each country's all-purpose energy is provided by 100 % wind, water, and sunlight (WWS). A weather model is used to predict wind and solar fields and building heat and cold loads. A grid model is used to match electricity, heat, cold, and hydrogen demand with WWS supply; electricity, heat, cold, and hydrogen storage; and demand response. Stable solutions are found for all countries, including the smallest (Luxembourg and Gibraltar) and largest (France, Germany, Spain, Italy, and the United Kingdom), and for all combinations of countries. Results indicate that interconnecting countries reduces aggregate annual energy costs, overbuilding of generators and storage, energy shedding, and land/water area requirements in most, but not all, situations. Interconnecting Western Europe may decrease aggregate annual energy costs ∼13 % relative to isolating each country. The best reductions are found by interconnecting hydropower-rich Norway with Denmark (20.6 %) and Northwestern Europe (13.7 %). Interconnecting the smallest countries, Luxembourg and Gibraltar, with larger countries benefits all countries. Whether isolated or interconnected, all countries examined, including France and Germany, can maintain a stable grid at low cost with 100 % WWS.

Application of Renewable Energy Sources Cathodic Protection and Their Economical Aspects.(Dept.E)

As cathodic protection systems are fed from 0.C. sources, a difficulty will be faced to find a suitable 0.c, source if such systems are used to protect petroleum tanks or pipe lines which lie in isolated areas far away from the existing transmission lines, Usually 3 methods could be adopted here: i) Installing a transmission link with a rectifier substation between the nearest convenient existing transmission line and the D.C. cathodic protection source. ii) Using private motor-generator sets; where the motor as a prime mover works by convenient fossil fuel. iii) Using storage battery systems, the capacity of which must be large enough to supply the required protective current during a period necessary for charging a second battery at the nearest charging station and replacing the one in use. In this case the charging battery system may he fed from rectifier substations, or private D.C. generating sots whose prime movers operate with conventional or non-conventional energy sources. This paper presents the limitations and conditions required for the conveniency of applying the non-conventional energy sources (photovoltaic) and their economical aspects in charging such batteries; together with examples of calculations clarifying the analytical steps and assumptions adopted in this study by means of which the final conclusions and results presented here were deduced. A simplified approach for the solar specific annual energy cost calculations using nomogram analysis and performance charts applied to local conditions in this respect is present od also in this paper.

An Artificial Intelligence Empowered Cyber Physical Ecosystem for Energy Efficiency and Occupation Health and Safety

Reducing energy waste is one of the primary concerns facing Remote Industrial Plants (RIP) and, in particular, the accommodations and operational plants located in remote areas. With the COVID-19 pandemic continuing to attack the health of workforce, managing the balance between energy efficiency and Occupation Health and Safety (OHS) in the workplace becomes another great challenge for the RIP. Maintaining this balance is difficult mainly because a full awareness of the OHS will generally consume more energy while reducing the energy cost may lead to a less effective OHS, and the existing literature has not seen a system that is designed for the RIPs to conserve energy usage and improve workforce OHS simultaneously. To bridge this gap, in this paper, we propose an AI Empowered Cyber Physical Ecosystem (AECPE) solution for the RIPs, which integrates Cyber-Physical Systems (CPS), artificial intelligence, and mobile networks. The preliminary results of lab experiments and field tests proved that the AECPE was able to help industries reduce the corporate annual energy cost that is worth millions of dollars, optimise the environmental conditions, and improve OHS for all workers and stakeholders. The implementation of the AECPE can result in efficient energy usage, reduced wastage and emissions, environment-friendly operations, and improved social reputation of the industries.

Comparative Analysis of Various Insulation Materials for Building Envelope Components

Due to growing environmental and economic concerns in recent years there has been a renewed interest in building energy efficiency as building contribute a huge consumption of energy across world. Among the effective and compatible ways of energy conservation technologies available today, insulation of buildings is most relevant as it also reduces negative environmental impacts and annual energy costs. The building envelope comprises of different components which are pre-dominant in evaluating thermal performance of a building. A proper selection of insulation materials results in a low energy demand process. In any material selection procedure, the ultimatum is of addressing material properties, parameters, criteria and performance characteristics. Hence this study aims to provide a knowledge base on identified insulation materials for corresponding building components with respect to material properties and performance parameters and recommend best material. Study presents comparative analysis of insulation options available for various building components.

A Comparative Analysis of Thermal Performance, Annual Energy Use, and Life Cycle Costs of Low-cost Houses Made with Mud Bricks and Earthbag Wall Systems in Sub-Saharan Africa

Given the high demand for low-cost housing by the low-income earners, coupled with the tropical climate experienced in sub-Saharan Africa, new-built housing stock needs utmost attention to cost, durability, and efficiency. With the walls accounting for a substantial proportion of the total building cost, choice of a wall system for use in building construction is critical. This choice usually depends on how durable, comfortable, ecological, and economical a given system is, to meet both the quality standards and low-cost aspects of housing. Although the earthbag building system allows for the construction of strong, affordable, and sustainable housing, it is not widely known. As such, its sustainable characteristics have gone unrecognised throughout the building industry. This paper examines and compares the thermal properties and total Life Cycle Costs (LCC) of earthbag walls with the commonly used burnt brick walls - based on the Degree-Days method and Life Cycle Costing analyses of building walls located in one of the hottest regions in Uganda. In-situ measurements of temperature and heat flux were conducted in accordance with ISO 9869 and the annual energy requirements obtained. The total LCC were calculated based on the initial construction costs and annual energy costs attributed to the building wall systems. Earthbags housing was found to be thermal-physically better than the brick wall with a lower U-value resulting in lower annual energy requirements and a huge saving in annual energy costs of up to 83.2%. This saving, coupled with low initial construction costs made the earthbag unit 68.7% cheaper than the burnt brick unit over a 30-year period. Therefore, this study findings suggest earthbag walling system as an economically viable and technically feasible low-cost construction option for rural areas and low-incomers earners’ housing in warm climatic conditions, a characteristic of sub-Saharan countries – so as to promote regional development.

Fleet and charging infrastructure decisions for fast-charging city electric bus service

Decision aspects concerning the introduction of fast-charging city electric buses are studied in this paper. The main studied problem consists of determining a fleet of electric buses and their charging infrastructure such that a social-ecological value is maximized. In the most representative time period, all the electric buses should be available to drive, the required inter-bus interval should be maintained, the output power of any charging station and transformer should not be exceeded, and the total capital cost and the total annual operating, depreciation and energy cost should not exceed certain maximum thresholds. The total passenger demand satisfied by the electric buses can be considered as the value to be maximized. A secondary problem consists of finding a passenger load balanced schedule of the vehicles on the same route. Mathematical models for these two problems are proposed. A randomized heuristic algorithm combined with the Particle Swarm Optimization is developed for the main problem, and a known polynomial time algorithm is adapted for the secondary problem. A case study for the city of Minsk (Belarus) and computer experiments with random instances are provided. The proposed approach delivered solutions with values deviating at most 12% on average and 24% in the worst case from the upper bounds obtained as optima of a relaxed problem.

Optimizing the thickness of a straw outer wall of a building for sows in a view to achieving cost-effective heat insulation

Abstract. The aim of the study is to determine the optimum thickness of the surrounding wall structure of a building for nursing sows by using heat insulation from straw and different fuel (pellets and dry wood) for heating the building. To achieve the purpose, 6 models of walls made of environmentally friendly panels with wooden skeleton, thermal insulation from pressed straw bales and double-sided clay plaster have been developed, such that the accepted thickness of the thermal insulation layer is respectively: 20, 25, 30, 35, 40 and 45 cm. The construction value of the finished wall is determined by adding the value of the construction and assembly works on the construction site to the value of the preparation of the panels (in a workshop), including the payment of labor, materials and additional costs for the implementation of clay plaster and waterproofing membrane. The annual energy losses through 1 m2 of the enclosing wall and the annual heat insulation costs (as a sum of annual energy cost and the depreciation deductions) are determined through the described methodology and verification of condensation of water vapor on the inner surface of the wall was carried out. The results of the research show that by using pellets for fuel, the optimal thickness of the thermal insulation is 45 cm, and by using dry wood it is 35, 40 and 45 cm. All studied models of enclosing straw wall meet the hygienic requirements for preventing condensation on their inner surfaces.

Economic Assessment and Control Strategy of Combined Heat and Power Employed in Centralized Domestic Hot Water Systems

With the increasing application of CHP and an industry transition to distributed energy, it is necessary to make a comprehensive economic analysis and comparison of the entire lifetime of CHP from the net present value (NPV), payback period, and cost-saving ratio (CSR). Five systems, including micro-CHP, gas boiler (GB), air-source heat pump (ASHP), domestic gas-fired heater and domestic electric hot water-heater, are simulated. First, this paper takes annual heat use efficiency (AHUE) into account to compare the economy of each domestic hot water (DHW) system. The results show that a domestic gas-fired heater system is the most economical option in the AHUE of 31.28%. The economic influence of CHP and gas-fired heater under different AHUE are then analyzed. The results show that the DHW system based on CHP is the best when the AHUE is more than 55.35%. Finally, three different operation strategies of CHP are considered in this paper. From the perspective of annual energy cost and payback, the internal combustion-based CHP with thermal energy system (TES) is superior to the other two strategies being studied. Considering the optimal economic benefits, the CSR of the three different operation strategies is 41.3%, 69.69% and 69.77%, respectively.

Optimal management of energy sharing in a community of buildings using a model predictive control

Exporting generated electricity by on-site renewable energy systems from buildings to the grid is only slightly profitable in many countries. Therefore, it is required to investigate the benefits of sharing generated energy in a microgrid within a community of buildings. Exploiting the benefits of peer-to-peer energy exchange between prosumers in a community can make the best use of the on-site generation while reducing their bills. This study elaborates the potential of energy management to minimize the electricity cost of a community consisted of multiple buildings and connected to a microgrid. To implement this, an energy management system is designed based on non-linear economic model predictive control and successive linear programming for sharing the on-site surplus generated electricity between the buildings in the community. Four buildings are simulated and studied as an example of a small community. These buildings are dissimilar in their age, thermal mass, insulation, heating system and on-site renewable energy systems. It is shown that considering the community of buildings as a single entity, the novel model predictive control can be efficiently used for minimizing the energy cost of the community that has various sources of energy generation, conversion and storage, including significant non-linear interactions. Three different scenarios of the energy management system for the studied community are investigated, and the results indicate that the annual electricity energy cost for single buildings can be reduced by 3.0% to 87.9%, depending on the building and its systems, and by 5.4% to 7.7% on the community level.

The energy savings impact of the existing building commissioning process by building type

This study presents the energy savings impact of the Continuous Commissioning® (CC®) version of the Existing Building Commissioning (EBCx) process in 197 projects (592 buildings) since the inception of the process in the early 1990s. These are the results of a comprehensive evaluation of the impact of EBCx projects. The evaluation of the impact of EBCx by building type included 316 education buildings, 141 health care facilities, 13 laboratory facilities, 32 office buildings, as well as 90 miscellaneous facilities. The annual energy cost savings, as of December 2016, exceeded $29.7 million (2017 $), for 197 EBCx projects (over 59 million ft2 (5.48 million m2) of area). The median annual cost savings were $0.24/ft2 ($2.26/m2) for individual education buildings, $0.40/ft2 ($4.31/m2) for individual health care facilities, $1.54/ft2 ($16.58/m2) for individual laboratory facilities, $0.59/ft2 ($6.35/m2) for individual office buildings, $0.50/ft2 ($5.38/m2) for individual miscellaneous facilities. The median percent savings for electricity were up to 14%, the demand savings up to 14%, the natural gas savings up to 33%, the CHW savings ranged from 21 to 36%, and the HW savings ranged from 28 to 71%. The median percent savings are remarkably consistent by building type.

Techno-economic analysis of heat recovery from supermarket’s CO2 refrigeration systems to district heating networks

Abstract This paper investigates the opportunity of utilizing the spare heating capacity of CO2 refrigeration systems in supermarkets to produce heat to be sold to district heating network operators. A comprehensive description and assessment of two control strategies that could be implemented to enable the heat export function are presented. To maximise the heating capacity during the coldest moments of the year, the integration of geothermal storage with the CO2 system was investigated as an additional scenario. The BIN method was used to perform annual energy calculations. Furthermore, a sensitivity analysis was carried out on the most critical parameters, namely the heating demand, price ratio and temperature levels of the district heating network. For the assumed prices and energy demands, the supermarket could make profits corresponding to up to 16% (10,000 €/year) of the annual energy cost by selling part of the heat recovered to the district heating network operator. Furthermore, the heat exported could save up to 18% of the annual CO2 emissions of the supermarket compared to the baseline. Finally, the sensitivity analysis showed that the economics of this solution is the more profitable, the lower return temperature of the heating network where the installation is connected.