Using Forecasted Daily Maximum Temperatures to Control a Chiller Thermal Storage System

2018 ◽  
Author(s):  
Christopher Baldwin ◽  
Cynthia A. Cruickshank
Keyword(s):  
Storage Tank ◽  
Residential Buildings ◽  
Storage System ◽  
Peak Load ◽  
Cost Savings ◽  
Thermal Storage ◽  
The United States ◽  
Daily Maximum ◽  
Cooling Load ◽  
Control Scheme

Residential buildings in Canada and the United States are responsible for approximately 20% of secondary energy consumption. Over the past 25 years, air conditioning has seen the single largest increase of any residential end use. This load currently places a significant peak load on the electrical grid during later afternoon periods during the cooling season. One method to reduce or eliminate this peak load being placed in the grid is the use of a chiller coupled with a thermal storage system. The chiller operates during off-peak periods, predominately over-night to charge the thermal storage tank, and the stored cooling potential is realized to meet the cooling loads during peak periods. In previous studies, the use of a chiller has seen a reduction in annual operating costs, however a significant increase in energy occurs as a result of decreased performance of the chiller. To improve system performance, a new control scheme was developed, which uses the forecasted daily high for the next day to predict the cooling load for the day during peak periods for the day. The predicted cooling load is then used as the set-point for the cold thermal storage tank, allowing the peak cooling load to be met using stored cooling potential. This control scheme was implemented into a modelled house located in each of the 7 major ASHRAE zones, with a storage tank with a previously found optimal tank volume. Across each of the locations, a reduction in annual utility costs and overall energy required to meet the building loads observed, with the total cost savings between 0.3% and 1.5% and total electricity required to meet the cooling demand decreasing by as much as 10.2%.

scholarly journals Sensitivity Analysis of Occupant Preferences on Energy Usage in Residential Buildings

2021 ◽  
Author(s):  
Kaleb Pattawi ◽  
Prateek Munankarmi ◽  
Michael Blonsky ◽  
Jeff Maguire ◽  
Sivasathya Pradha Balamurugan ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Thermal Comfort ◽  
Residential Buildings ◽  
Electricity Consumption ◽  
Cost Savings ◽  
The United States ◽  
Comfort Level ◽  
Electrical Grid ◽  
Home Energy Management ◽  
The Impact

Abstract Residential buildings, accounting for 37% of the total electricity consumption in the United States, are suitable for demand response (DR) programs to support effective and economical operation of the power system. A home energy management system (HEMS) enables residential buildings to participate in such programs, but it is also important for HEMS to account for occupant preferences to ensure occupant satisfaction. For example, people who prefer a higher thermal comfort level are likely to consume more energy. In this study, we used foresee™, a HEMS developed by the National Renewable Energy Lab (NREL), to perform a sensitivity analysis of occupant preferences with the following objectives: minimize utility cost, minimize carbon footprint, and maximize thermal comfort. To incorporate the preferences into the HEMS, the SMARTER method was used to derive a set of weighting factors for each objective. We performed week-long building energy simulations using a model of a home in Fort Collins, Colorado, where there is mandatory time-of-use electricity rate structure. The foresee™ HEMS was used to control the home with six different sets of occupant preferences. The study shows that occupant preferences can have a significant impact on energy consumption and is important to consider when modeling residential buildings. Results show that the HEMS could achieve energy reduction ranging from 3% to 21%, cost savings ranging from 5% to 24%, and carbon emission reduction ranging from 3% to 21%, while also maintaining a low thermal discomfort level ranging from 0.78 K-hour to 6.47 K-hour in a one-week period during winter. These outcomes quantify the impact of varying occupant preferences and will be useful in controlling the electrical grid and developing HEMS solutions.

Volume Sizing for Thermal Storage With Phase Change Material for Concentrated Solar Power Plant

2014 ◽  
Author(s):  
Ben Xu ◽  
Peiwen Li ◽  
Cholik Chan
Keyword(s):  
Power Plant ◽  
Phase Change ◽  
Phase Change Material ◽  
Storage Tank ◽  
Solar Power ◽  
Heat Storage ◽  
Storage System ◽  
Thermal Storage ◽  
Concentrated Solar Power ◽  
Change Material

With a large capacity thermal storage system using phase change material (PCM), Concentrated Solar Power (CSP) is a promising technology for high efficiency of solar energy utilization. In a thermal storage system, a dual-media thermal storage tank is typically adopted in industry for the purpose of reducing the use of the heat transfer fluid (HTF). While the dual-media sensible heat storage system has been well studied, a dual-media latent heat storage system (LHSS) still needs more attention and study; particularly, the sizing of volumes of storage tanks considering actual operation conditions is of significance. In this paper, a strategy for LHSS volume sizing is proposed, which is based on computations using an enthalpy-based 1D model. One example of 60MW solar thermal power plant with 35% thermal efficiency is presented. In the study, potassium hydroxide (KOH) is adopted as PCM and Therminol VP-1 is used as HTF. The operational temperatures of the storage system are 390°C and 310°C, respectively for the high and low temperatures. The system is assumed to operate for 100 days with 6 hours charge and 6 hours discharge every day. From the study, the needed height of the thermal storage tank is calculated from using the strategy of tank sizing. The method for tank volume sizing is of significance to engineering application.

Experimental Exploration of a Small Scale Pneumatically Pumped Thermal Storage System

2016 ◽  
Author(s):  
Inri Rodriguez ◽  
Jesus Cerda ◽  
Daniel S. Codd
Keyword(s):  
High Temperature ◽  
Storage Tank ◽  
Pulse Width Modulation ◽  
Low Cost ◽  
Storage System ◽  
Heat Engine ◽  
Thermal Storage ◽  
Heat Transfer Fluid ◽  
Small Scale ◽  
Constant Frequency

A prototype water-glycerol two tank storage system was designed to simulate the fluidic properties of a high temperature molten salt system while allowing for room temperature testing of a low cost, small scale pneumatically pumped thermal storage system for use in concentrated solar power (CSP) applications. Pressurized air is metered into a primary heat transfer fluid (HTF) storage tank; the airflow displaces the HTF through a 3D printed prototype thermoplate receiver and into a secondary storage tank to be dispatched in order to drive a heat engine during peak demand times. A microcontroller was programmed to use pulse-width modulation (PWM) to regulate air flow via an air solenoid. At a constant frequency of 10Hz, it was found that the lowest pressure drops and the slowest flowrates across the receiver occurred at low duty cycles of 15% and 20% and low inlet air pressures of 124 and 207 kPa. However, the data also suggested the possibility of slug flow. Replacement equipment and design modifications are suggested for further analysis and high temperature experiments. Nevertheless, testing demonstrated the feasibility of pneumatic pumping for small systems.

Energy Storage Start-up Strategies for Concentrated Solar Power Plants With a Dual-Media Thermal Storage System

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Ben Xu ◽  
Peiwen Li ◽  
Cho Lik Chan
Keyword(s):  
Energy Storage ◽  
Storage Tank ◽  
Heat Storage ◽  
Storage System ◽  
Electrical Energy ◽  
Thermal Storage ◽  
Energy Output ◽  
Concentrated Solar Power ◽  
Start Up ◽  
Hot Start

A concentrated solar power (CSP) plant typically has thermal energy storage (TES), which offers advantages of extended operation and power dispatch. Using dual-media, TES can be cost-effective because of the reduced use of heat transfer fluid (HTF), usually an expensive material. The focus of this paper is on the effect of a start-up period thermal storage strategy to the cumulative electrical energy output of a CSP plant. Two strategies—starting with a cold storage tank (referred to as “cold start”) and starting with a fully charged storage tank (referred to as “hot start”)—were investigated with regards to their effects on electrical energy production in the same period of operation. An enthalpy-based 1D transient model for energy storage and temperature variation in solid filler material and HTF was applied for both the sensible heat storage system (SHSS) and the latent heat storage system (LHSS). The analysis was conducted for a CSP plant with an electrical power output of 60 MWe. It was found that the cold start is beneficial for both the SHSS and LHSS systems due to the overall larger electrical energy output over the same number of days compared to that of the hot start. The results are expected to be helpful for planning the start-up operation of a CSP plant with a dual-media thermal storage system.

scholarly journals Numerical Simulation of Phase Change Material Composite Wallboard in a Multi-Layered Building Envelope

2012 ◽  
Author(s):  
Stephen D. Zwanzig ◽  
Yongsheng Lian ◽  
Ellen G. Brehob
Keyword(s):  
Energy Consumption ◽  
Boundary Conditions ◽  
Phase Change ◽  
Latent Heat ◽  
Residential Buildings ◽  
Peak Load ◽  
The United States ◽  
Building Envelope ◽  
Latent Heat Storage ◽  
Exterior Boundary

Residential buildings account for a large portion of total energy consumption in the United States. Residential energy usage can be dramatically reduced by improving the efficiency of building envelope systems. One such method is to incorporate thermally massive construction materials into the building envelope. This benefits building operation by reducing the energy requirement for maintaining thermal comfort, downsizing the AC/heating equipment, and shifting the peak load from the electrical grid. When impregnated or encapsulated into wallboard or concrete systems, phase change materials (PCMs) can greatly enhance their thermal energy storage capacity and effective thermal mass. In this work we numerically study the potential of PCM on energy saving for residential homes. For that purpose we solve the one-dimensional, transient heat equation through the multi-layered building envelope using the Crank-Nicolson discretization scheme. The latent heat storage of the PCM was accounted for with a phase fraction in a latent heat source term. Using this code we examine a PCM composite wallboard incorporated into the walls and roof of a typical residential building across various climate zones. The PCM performance was studied under all seasonal conditions using the latest typical meteorological year (TMY3) data for exterior boundary conditions. Comparisons were made between different PCM wallboard locations. Our work shows that there is an optimized location for PCM placement within building envelope surfaces dependent upon the resistance values between the PCM layer and the exterior boundary conditions. We further identified the energy savings potential by comparing the performance of the PCM wallboard against the performance of a building envelope without PCM. Our study shows that PCM composite wallboard can reduce the energy consumption in summer and winter and can shift the peak electricity load in the summer.

Home Energy Management System (HEMS): Coupled Flexible Load Management in Homes

2021 ◽  
Author(s):  
Yilin Jiang ◽  
Li Song ◽  
Janet K. Allen ◽  
Farrokh Mistree
Keyword(s):  
Decision Support ◽  
Energy Management ◽  
Management System ◽  
Residential Buildings ◽  
Peak Load ◽  
Cost Savings ◽  
Load Management ◽  
Energy Management System ◽  
Home Energy Management ◽  
Home Energy Management System

Abstract Electricity suppliers have introduced time-of-use (TOU) metering and pricing in residential buildings in recent years. By increasing the price of electricity during on-peak hours (e.g., 2 pm to 7 pm in summer months), suppliers expect to regulate the energy usage from homeowners when the grid is near capacity. Therefore, homeowners are motivated to shift the load by moving their home electricity use from on-peak hours to off-peak hours for utility cost savings. However, peak load management is another factor that needs to be considered, since a higher peak load might cause other penalties, such as making suppliers change their current tariff policy in the next paying period since the grid needs to fulfill a higher demand. In this paper we explore the Home Energy Management System (HEMS) Strategy for homeowners who are considering saving money by reducing/avoiding the on-peak hour electricity usage while reducing peak load. A multi-goal scheduling problem is solved by constructing a coupled compromise decision support problem in which a water heater is coupled with flexible, non-thermal appliances such as a washing machine. To address these multiple goals, we use Decision Support Problem (DSP) construct. A use case simulation shows that our scheduler can make a reasonable tradeoff between two conflicting goals, helping the homeowner save money while maintaining low peak demand.

Cold Thermal Energy Storage

2017 ◽  
pp. 93-123
Author(s):  
Franc Franc Kosi ◽  
Branislav Zivkovic ◽  
Mirko S. Komatina ◽  
Dragi Antonijevic ◽  
Mohamed Abdul Galil ◽  
...  
Keyword(s):  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage System ◽  
Thermal Storage ◽  
Cooling Load ◽  
Air Conditioning System ◽  
Operational Characteristics ◽  
Calculated Load ◽  
Operating Strategies

The chapter gives an overview of cold thermal energy storage (CTES) technologies. Benefits as well as classification and operating strategies of CTES are discussed. Design consideration and sizing strategies based on calculated load profile for design day is presented. Some recommendation concerning designing of CTES equipment are given. Special attention was paid to the analysis of specific features of heat transfer phenomena in ice storage tank including the assessment of the duration and the rate of ice formation and melting. The methodology of sizing components of the ice thermal storage system included in an air conditioning system for an office building situated in hot wet and dry climate are presented. Based on hourly cooling load calculation that was carried out using Carrier's Hourly Analysis Program, sizing of ice thermal storage system for different operating strategies included full, chiller priority and ice priority storage operation for the design day are presented. Finally, an analysis of some operational characteristics of the system are analyzed.

Energy and Cost Minimal Control of Active and Passive Building Thermal Storage Inventory

2005 ◽  
Vol 127 (3) ◽  
pp. 343-351 ◽  
Author(s):  
Gregor P. Henze
Keyword(s):  
Optimal Control ◽  
Energy Consumption ◽  
Thermal Energy ◽  
Peak Load ◽  
Cost Savings ◽  
Electrical Energy ◽  
Thermal Storage ◽  
Coefficient Of Performance ◽  
Electrical Energy Consumption ◽  
Electricity Cost

In contrast to building energy conversion equipment, less improvement has been achieved in thermal energy distribution, storage and control systems in terms of energy efficiency and peak load reduction potential. Cooling of commercial buildings contributes significantly to the peak demand placed on an electrical utility grid and time-of-use electricity rates are designed to encourage shifting of electrical loads to off-peak periods at night and on weekends. Buildings can respond to these pricing signals by shifting cooling-related thermal loads either by precooling the building’s massive structure (passive storage) or by using active thermal energy storage systems such as ice storage. Recent theoretical and experimental work showed that the simultaneous utilization of active and passive building thermal storage inventory can save significant amounts of utility costs to the building operator, yet increased electrical energy consumption may result. The article investigates the relationship between cost savings and energy consumption associated with conventional control, minimal cost and minimal energy control, while accounting for variations in fan power consumption, chiller capacity, chiller coefficient-of-performance, and part-load performance. The model-based predictive building controller is employed to either minimize electricity cost including a target demand charge or electrical energy consumption. This work shows that buildings can be operated in a demand-responsive fashion to substantially reduce utility costs with marginal increases in overall energy consumption. In the case of energy optimal control, the reference control was replicated, i.e., if only energy consumption is of concern, neither active nor passive building thermal storage should be utilized. On the other hand, cost optimal control suggests strongly utilizing both thermal storage inventories.

Optimal Design of a Molten Salt Thermal Storage Tank for Parabolic Trough Solar Power Plants

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
R. Gabbrielli ◽  
C. Zamparelli
Keyword(s):  
Optimal Design ◽  
Molten Salt ◽  
Storage Tank ◽  
Power Plants ◽  
Storage System ◽  
Thermal Storage ◽  
Parabolic Trough ◽  
Investment Cost ◽  
Total Investment ◽  
Solar Power Plants

This paper presents an optimal design procedure for internally insulated, carbon steel, molten salt thermal storage tanks for parabolic trough solar power plants. The exact size of the vessel and insulation layers and the shape of the roof are optimized by minimizing the total investment cost of the storage system under three technical constraints: remaining within the maximum allowable values of both temperature and stress in the steel structure, and avoiding excessive cooling and consequent solidification of the molten salt during long periods of no solar input. The thermal, mechanical and economic aspects have been integrated into an iterative step-by-step optimization procedure, which is shown to be effective through application to the case study of a 600MWh thermal storage system. The optimal design turns out to be an internally insulated, carbon steel storage tank characterized by a maximum allowable height of 11m and a diameter of 22.4m. The total investment cost is about 20% lower than that of a corresponding AISI 321H stainless steel storage tank without internal protection or insulation.

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