Potential Energy Cost Savings Research Articles

Utility-based context-aware multi-agent recommendation system for energy efficiency in residential buildings

A significant part of CO2 emissions is due to high electricity consumption in residential buildings. Using load shifting can help to improve the households’ energy efficiency. To nudge changes in energy consumption behavior, simple but powerful architectures are vital. This paper presents a novel algorithm of a recommendation system generating device usage recommendations and suggests a framework for evaluating its performance by analyzing potential energy cost savings. As a utility-based recommender system, it models user preferences depending on habitual device usage patterns, user availability, and device usage costs. As a context-aware system, it requires an external hourly electricity price signal and appliance-level energy consumption data. Due to a multi-agent architecture, it allows for easy integration of new agents, enabling seamless functionality expansion, or the disabling of existing agents to tailor the system to specific needs. Empirical results show that the system can provide energy cost savings of 18% and more for most studied households.

Simultaneous Cr(VI) Reduction and Dexamethasone Phosphate Oxidation with Organo-metallic Sludge Formation Under UV Irradiation: Kinetics, Degradation Pathways, and Mechanism

In this study, we investigated the concurrent elimination of two distinct contaminants: organic matter in the form of dexamethasone phosphate (DexP) and an inorganic substance, chromium (Cr), employing UV irradiation. UV irradiation serves as a potent tool for breaking down organic materials, leading to the production of benign by-products, namely CO2 and H2O. Under optimal conditions characterized by a 30:1 DexP/Cr molar ratio and a pH level of 9, remarkable removal efficiencies were attained. In a mere 20 min, approximately 100% of DexP and 82.73% of Cr were effectively removed. Intriguingly, the removal of Cr exhibited an initially sluggish rate, with deposition commencing only after the breakdown of the DexP structure. This transformation was accompanied by the emergence of various sludge forms, each possessing unique characteristics. Utilizing Fourier-transform infrared (FTIR) analysis, we identified these sludge forms as chromium(III) hydroxide (green sludge), chromium(III) hydroxide (brown sludge), chromium(III) oxide (tiny green crystals), chromium(II) acetate chromium trioxide (red brick), and chromium oxide (black sludge). Further experimentation with varying concentrations of Cr and DexP, ranging from 50 to 150 mg L−1, yielded a range of rate constants (kobs) from 0.33 to 0.15 and removal efficiencies (robs) from 16.8 to 23.4% in the UV/DexP/Cr process. Energy efficiency output (EEO) calculations revealed that Cr precipitation ranged from 24.65 to 5.74 kW h m−3, whereas DexP EEO ranged from 12.54 to 4.73 kW h m−3. Of significant importance is the observation that when these two contaminants are removed simultaneously, the overall energy consumption is substantially lower compared to the scenario where pollutants are addressed individually. This finding underscores the efficiency and potential energy cost savings achievable through the concurrent removal of DexP and Cr using UV irradiation, making it a promising approach for environmental remediation.

Maximising the benefit of variable speed heat-pump water heater with rooftop PV and intelligent battery charging

Domestic applications of thermal energy storage, interacting with rooftop PV and batteries can substantially reduce consumer electricity costs, whilst assisting grid stability. Air source heat pump water heaters (HPs) with inherent thermal storage offer significant purchased energy savings, however, their typical control only considers stored water temperature. We demonstrate that further energy and cost reductions are possible using variable compressor speed controls that optimise thermal performance in real-time, whilst coordinating energy consumption to match available PV or shifting consumption to off-peak hours. The incremental complexity of variable-speed HP water heaters can reduce HP electricity consumption from the grid by up to 28% without PV or battery, 88% with PV, and 99% using PV and battery storage. By integrating the HP and all other domestic electrical loads, we exploit the combination of thermal and battery energy storage using rules-based and machine-learnt hierarchical controls to reduce the net household energy cost. Machine-learnt grid battery charging is shown to reduce annual grid energy consumption by 84%, delivering 99% of the potential energy cost savings. We conclude that a HP with inherent thermal storage, interacting with rooftop PV offers the most cost-effective home energy storage solution, lowering net lifetime costs by up to 27%.

Cost and Heat Integration Analysis for CO2 Removal Using Imidazolium-Based Ionic Liquid-ASPEN PLUS Modelling Study

The recent advancement in efficient and recoverable CO2 capture solvents has been stimulated by the environmental harm resulting from the accumulation of greenhouse gases. Ionic liquids (ILs) and IL-based solvents have given rise to a novel method of CO2 collection that is highly efficient, economical, and environmentally benign. However, there is a lack of knowledge about the implementation of this process on a wider scale, and it has limitations, including high solvent costs. This simulated study shows that [EMIM][NTF2] can remove up to 99.4% of the CO2 from industrial waste effluents using three distinct compositions. Following an economic study using a 20-year plant life estimate, with a plant capacity of 4000 kg/h (206.165 kmol/h) for the raw mixed stream flow (inlet) and a maximum CO2 capacity of 38.1 kmol/h, it was determined that the process’s overall annualized cost was USD 2.1 million with operating expenses being USD 1.8 million. The Aspen Activated Energy Analysis’s recommendation of adding a heat exchanger, with a payback year of 0.0586 years, a 23.34 m2 area, and potential energy cost savings of USD 340,182/Year was also implemented successfully. These findings propose a conceptual framework for the development of novel ionic liquids for CO2 capture. It also demonstrates that sustainable [EMIM][Tf2N]-based absorption techniques for CO2 capture have the potential to be an industrial technology.

Evaluation of Dynamic Insulation Systems for Residential Buildings in Barcelona, Spain

Abstract This paper evaluates the potential energy cost savings when high R-value static insulation layers as well as dynamic insulation materials (DIMs) are applied to residential housing located in Barcelona Spain. The analysis considers three dwelling prototypes to characterize the existing housing stock in Barcelona including detached attached and apartments. In addition three vintages for each housing prototype are defined: before 1979 when building envelope insulation took effect in Spain between 1980 and 2006 and after 2006 when the building envelope insulation code became more restrictive. Using a modified 3R2C network model to determine thermal loads the performance of both static and dynamic insulation systems is evaluated when applied to exterior wall for various housing prototypes in Barcelona. The dynamic insulation R-value is selected based on a 2-step control strategy. The analysis results indicate that DIMs with the largest R-value step (i.e. difference between the high and the low R-values) achieve the highest savings in source energy reaching up to 19% reduction in source heating and cooling energy for the entire housing stock of Barcelona. The annual energy savings achieved by DIMs are valued to be 181 M€/year for the entire existing housing stock in Barcelona. In addition electrical peak demand reduction associated with retrofitting exterior walls for the existing Barcelona housing stock can result in future avoidance of building new power plants and can provide additional 144 M€ and 162 M€ for respectively static and dynamic insulation systems. Considering the current energy mix applying dynamic wall insulation systems for Barcelona existing housing stock could reduce annual CO2 emissions by more than 300 000 tons or 6.80% of the total carbon dioxide currently emitted to heat and cool homes.

Moore vs. Murphy: Tradeoffs between complexity and reliability in distributed energy system scheduling using software-as-a-service

Software-based optimization of building control strategies, including scheduling, has the potential to improve the performance of existing complex heating, ventilation, and air conditioning (HVAC), storage, and other systems—especially if temporally variable energy production, such as solar thermal or photovoltaics, is included. If reductions in energy bills can be achieved using optimized control strategies that take advantage of cost-saving opportunities, such as time-of-use pricing, the additional bill savings can cover further efficiency investment costs. As computer processing becomes cheaper over time (Moore’s Law), opportunities to perform complex control optimization become more abundant, and these can be performed remotely as software-as-a-service (SaaS). However, by “perfecting” our control strategies, we run an increased risk that when something unexpected happens (Murphy’s Law), the consequences of failure are greater. This study used simulation to explore the potential benefits of HVAC schedule optimization, delivery, and implementation using a SaaS paradigm, at various levels of complexity. Implementing optimal schedules in a model of an efficient building’s HVAC system, the study predicts energy cost savings of up to 10% compared to the naïve reference control strategy. Optimizing more system control variables increases the potential energy cost savings; however, these savings could be compromised by failures in communication inherent in delivering schedules via SaaS. The additional cost of energy resulting from the risk of increased demand charges generally increased with increased communication failure to a much larger extent than the risk of increased energy use charges. This work suggests that moderate improvements in performance, achieved at low cost by simple means, may be more effective than highly optimized schemes, which are more susceptible to failure due to their dependence on complex interactions between systems.

The Economics of Biomass Logistics and Conversion Facility Mobility: An Oregon Case Study

Abstract. This article presents an analysis of transportable biomass conversion facilities to evaluate the conceptual and economic viability of a highly mobile and modular biomass conversion supply chain in the Pacific Northwest of the United States. The goal of this work is to support a broader effort to more effectively and sustainably use residual biomass from commercial harvesting operations that are currently piled and burned as part of site preparation. A structural representation is first developed to include sources of biomass feedstock, distributed preprocessing hubs (centralized landings), and centralized processing facilities (biomass to product conversion sites) to produce desired products and byproducts. A facility costing model was developed to evaluate potential economics of scale, which then informed the optimization study. A mixed integer linear programming model was developed to characterize, evaluate, and optimize biomass collection, extraction, logistics, and facility placement over a regional landscape from a strategic level to evaluate the mobility concept. The objective was to minimize supply chain operational costs in order to quantify financial advantages and identify challenges of the proposed system modularity and mobility. A Lakeview, Oregon case study was evaluated with an assumed modular biochar facility servicing the region. In particular, we review economies of scale, mobility, energy costs, and biomass availability tradeoffs. This analysis points towards a modular system design of movement frequency between 1 to 2 years being most viable in the conditions evaluated. It was found that the impact of plant movement, scale, and biomass availability can increase supply chain costs by $11/BDMT ($10/BDT), $33/BDMT ($30/BDT), and $22/BDMT ($20/BDT) above the base case cost of $182/BDMT ($165/BDT) for a large-scale facility [45,000 BDMT yr-1(50,000 BDT yr-1)]in the conditions evaluated. Additionally, potential energy cost savings of a non-mobile modular stationary site as compared to one which utilizes off-grid electrical powers about $11/BDMT ($10/BDT) for a biochar facility. From the cases evaluated, a large-scale plant with limited mobility would be preferred under low availability of biomass conditions, whereas a stationary grid-connected plant would be more cost effective under higher availability conditions. Results depend greatly on the region, assumed harvest schedule, biomass composition, and governing biomass plant assumptions. Keywords: Biomass products, Biomass supply, Facility location, Mixed integer programming, Strategic planning, Transportable plants.

Assessment of variable speed pumps in water distribution systems considering water leakage and transient operations

In this study, the potential economic and hydraulic benefits of utilizing variable speed pumps (VSPs) in water supply systems are reported. A simple water distribution network simulation is carried out by EPANET and Bentley HAMMER models to examine variable speed operation. It was found that using VSPs could control and improve performance of the water distribution systems. Where the potential energy cost savings realized by installing variable speed drives is a significant value (about 20%), in addition the leakage reduces by 21% compared to constant speed pumps. Also, this approach can improve and control undesired and damaged surge pressures and water leakage resulting from the abnormal operation conditions accompanied by the fixed speed pumping.

The market value of energy efficiency in buildings and the mode of tenure

Concerns about global warming and growing scarcity of fossil fuels require substantial changes in energy consumption patterns and energy systems, as targeted by many countries around the world. One key element to achieve such transformation is to increase energy efficiency of the housing stock. In this context, it is frequently argued that private investments are too low in the light of the potential energy cost savings. However, heterogeneous incentives to invest in energy efficiency, especially for owner-occupants and landlords, may serve as one explanation. This is particularly important for countries with a large rental sector, like Germany. Nevertheless, previous literature largely focuses on the payoffs owner-occupants receive, leaving out the rental market. This paper addresses this gap by comparing the capitalisation of energy efficiency in selling prices and rents, for both types of residences. For this purpose data from the Berlin housing market are analysed using hedonic regressions. The estimations reveal that energy efficiency is well capitalised in apartment prices and rents. The comparison of implicit prices and the net present value of energy cost savings/rents reveals that investors anticipate future energy and house price movements reasonably. However, in the rental segment, the value of future energy cost savings exceeds tenants’ implicit willingness to pay by a factor of 2.5. This can either be interpreted as a result of market power of tenants, uncertainty in the rental relationship or the ‘landlord–tenant dilemma’.

Stochastic Programming Applied to EV Charging Points for Energy and Reserve Service Markets

A more realistic management of electric vehicle (EV) charging points requires to cope with stochastic behavior on vehicle staying patterns. This paper presents a stochastic programming model to achieve optimal management taking into account price variation in day-ahead and intraday electricity markets, together with regulating reserve margins. In this model, first-stage decisions determine day-ahead energy purchases and sales and the upward and downward reserve margins committed. Second-stage decisions correspond to intraday markets and deal with reserve requirements and several possible scenarios for vehicle staying pattern. The design of the objective function prioritizes supplying energy to EV batteries while minimizing the net expected energy cost at the EV charging point. A case study describing a parking for 50 EVs is analyzed. The case includes household, commercial and mixed EV staying patterns with several intraday arrival and departure scenarios. Pure and hybrid EVs are included, taking into account their respective energy characteristics. Sensitivity analysis is used to show the potential energy cost savings and the impact of different non-supply penalizations. The case study considers several vehicle staying patterns, energy price profiles and discharge allowances. The model achieves energy cost reductions between 1% and 15% depending on the specific case. A model validation by simulation has been done.

Small might be beautiful, but bigger performs better: Scale economies in “green” refurbishments of apartment housing

The energy efficiency of the residential housing stock plays a key role in strategies to mitigate climate change and global warming. In this context, it is frequently argued that private investment and the quality of thermal upgrades are too low in the light of the challenges faced and the potential energy cost savings. While many authors address the potential barriers for investors to increase energy efficiency, studies on the capabilities of different investors to reduce energy requirements of their property are scarce. This study investigates potential advantages of housing company's size, i.e. economies of scale, economies of scope and institutional learning in thermal upgrades of residential housing. Based on unique data on energy consumption in 102,307 apartment buildings in Germany, we present new evidence for the advantages and disadvantages of a housing company's size in “green” retrofitting projects. Our estimations show, that large housing companies outperform private landlords by far in high effort refurbishment projects. In contrast, private landlords appear to have advantages in low effort, incremental refurbishment activities. We demonstrate that a substantial share of the advantages of larger firms can be associated with specialization (i.e. repeated projects). The results offer new options for policy makers to refine the support schemes toward a low carbon housing stock.

Small Might Be Beautiful, But Bigger Performs Better: Scale Economies in 'Green' Refurbishments of Apartment Housing

The energy efficiency of the residential housing stock plays a key role in strategies to mitigate climate change and global warming. In this context, it is frequently argued that private investment and the quality of thermal upgrades is too low in the light of the challenges faced and the potential energy cost savings. While many authors address the potential barriers for investors to increase energy efficiency, studies on the capabilities different investors have to reduce energy requirements of their property are scarce. This study investigates potential advantages of housing company's size, i.e. economies of scale, economies of scope and institutional learning in thermal upgrades of residential housing. Based on unique data on energy consumption in 102,307 apartment houses in Germany, we present new evidence for advantages and disadvantages of housing company's size in "green" retrofitting projects. Our estimations show, that large housing companies outperform private landlords by far in high effort refurbishment projects. In contrast, private landlords appear to have advantages in low effort, incremental refurbishment activities. The results offer new options for policy makers to refine the support schemes towards a low carbon housing stock.

The Market Value of Energy Efficiency in Buildings and the Mode of Tenure

Concerns about global warming and growing scarcity of fossile fuels require substantial changes in energy consumption patterns and energy systems, as targeted by many countries around the world. One key element to achieve such transformation is to increase energy efficiency of the housing stock. In this context, it is frequently argued that private investments are too low in the light of the potential energy cost savings. However, heterogenous incentives to invest in energy efficiency, particularly for owner-occupants and landlords, may serve as one explanation. This is particularly important for countries with a large rental sector, like Germany. Nevertheless, previous literature largely focuses on the pay offs owner-occupants receive, leaving out the rental market. This paper addresses this gap by comparing the capitalization of energy efficiency in selling prices (rents) for both types of residences. For this purpose data from the Berlin housing market are analyzed in hedonic regressions. The estimations reveal that energy efficiency is well capitalized in apartment prices and rents. The comparison of implicit prices and the net present value of energy cost savings/rents reveals that investors anticipate future energy and house price movements reasonably. However, in the rental segment, the value of future energy cost savings exceeds tenants' implicit willingness to pay by factor 2.98. This can either be interpreted as a result of market power of tenants, uncertainty in the rental relationship, or the "landlord-tenant dilemma."

ESCOs and In–house Energy Managers: A Winning Team

ABSTRACT Over past 25+ years, energy service companies (ESCOs) have emerged as a successful way of carrying out energy efficiency improvements in industrial and institutional facilities. At the same time, facilities are entrusting their energy manager (EM) with the responsibility of reducing energy costs without fail However, this is often not accompanied by investment capital or people support from management, or at least not in proportion to the task assignment. One channel of supporting the EM is through use of ESCOs in forming a “partnering” arrangement to reduce both facility operating costs as well as provide for infrastructure needs without new capital outlay approvals by the corporation, and doing this rapidly. To make this partnership a success, EMs and ESCOs need to complement each other by bringing their respective strengths to bear on a potential energy cost savings project. The EMs can help in optimizing project planning and the swift corporate approval process, and the ESCO can bring focused expertise at practical energy efficiency opportunities suited to the client, and a keen focus on swiftly completing measures for the mutual benefit of the owner and the ESCO. This article addresses the EM/ESCO partnership, along with a recent successful case study.

Current cost and performance requirements for residential cool-storage systems

Cool-storage systems have the potential to reduce the overall cost of cooling for residential customers by shifting all or part of the electric load occurring during peak-demand periods to off-peak periods, thus lowering the total electrical bill where time-of-day (TOD) rates exist. The potential energy cost savings are substantial. In some U.S. locales (e.g., within the districts served by Oklahoma Gas and Electric, Arkansas Power and Light, and Wisconsin Electric Power), the difference between the peak and off-peak energy charges are >$0.100/kWh. This savings potential is the primary driving force for developing cool-storage systems for residential applications. This study establishes the current cost and performance requirements that make residential cool-storage technologies economically competitive with conventional residential air-conditioning systems. The results are based on the characteristics of conventional air-conditioning equipment and residential TOD rate structures existing during 1986–1987. Initial capital cost and annual coefficient of performance requirements for cool-storage systems were calculated for three U.S. cities with different climates and utility-rate structures. Both new construction and retrofits were considered.