Combined Solar and Internal Load Effects on Selection of Heat Reclaim-Economizer HVAC Systems

1990 ◽  
Vol 112 (2) ◽  
pp. 82-89
Author(s):  
Harry J. Sauer ◽  
Ronald H. Howell ◽  
Zijie Wang
Keyword(s):  
Heat Recovery ◽  
Energy Savings ◽  
Operating Time ◽  
Internal Heat ◽  
Hvac Systems ◽  
Load Level ◽  
Internal Load ◽  
Recovery System ◽  
Load Effects ◽  
Building Heat

The concern for energy conservation has led to the development and use of heat recovery systems which reclaim the building internal heat before it is discarded in the exhaust air. On the other hand, economizer cycles have been widely used for many years in a variety of types of HVAC systems. Economizer cycles are widely accepted as a means to reduce operating time for chilling equipment when cool outside air is available. It has been suggested that heat reclaim systems should not be used in conjunction with an HVAC system which incorporates an economizer cycle because the economizer operation would result in heat being exhausted which might have been recovered. Others suggest that the economizer cycle can be used economically in a heat recovery system if properly controlled to maintain an overall building heat balance. This study looks at potential energy savings of such combined systems with particular emphasis on the effects of the solar load (amount of glass) and the internal load level (lights, people, appliances, etc.). For systems without thermal storage, annual energy savings of up to 60 percent are predicted with the use of heat reclaim systems in conjunction with economizers when the heat reclaim has priority. These results strongly demonstrate the necessity of complete engineering evaluations if proper selection and operation of combined heat recovery and economizer cycles are to be obtained. This paper includes the basic methodology for making such evaluations.

scholarly journals A Method for Simulating Heat Recovery Systems Using AirModel in Implementations of the ASHRAE Simplified Energy Analysis Procedure

2011 ◽  
Vol 250-253 ◽  
pp. 3083-3089
Author(s):  
Cheng Gang Liu ◽  
Guang Hua Wei ◽  
Homer L. Bruner
Keyword(s):  
Heat Recovery ◽  
Energy Savings ◽  
Energy Analysis ◽  
Energy Systems ◽  
Hvac Systems ◽  
Analysis Procedure ◽  
Specific Input ◽  
Duct Systems ◽  
Recovery System ◽  
Heat Recovery System

A method for simulating heat recovery systems using AirModel in implementations of the ASHRAE simplified energy analysis procedure was developed in this paper. AirModel, a simulation tool used to simulate the energy consumption of building heating, ventilating, and air-conditioning (HVAC) systems, was developed by the Energy Systems Laboratory (ESL) at Texas A&M University (TAMU) in the 1990’s. This program is capable of simulating single duct reheat systems and dual duct systems with economizer cycles. However, in certain buildings, energy savings techniques such as heat recovery systems are implemented but AirModel does not have a specific input to simulate this system. Presented in this paper is a method to simulate a heat recovery system using AirModel. An example of this methodology was used to simulate the HVAC system with a heat recovery system for the Biophysics and Biochemistry building on the TAMU campus.

scholarly journals A Computer Vision-Based Occupancy and Equipment Usage Detection Approach for Reducing Building Energy Demand

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 156
Author(s):  
Paige Wenbin Tien ◽  
Shuangyu Wei ◽  
John Calautit
Keyword(s):  
Deep Learning ◽  
Real Time ◽  
Energy Demand ◽  
Energy Savings ◽  
Internal Heat ◽  
Electrical Equipment ◽  
Building Energy ◽  
Hvac Systems ◽  
Equipment Usage

Because of extensive variations in occupancy patterns around office space environments and their use of electrical equipment, accurate occupants’ behaviour detection is valuable for reducing the building energy demand and carbon emissions. Using the collected occupancy information, building energy management system can automatically adjust the operation of heating, ventilation and air-conditioning (HVAC) systems to meet the actual demands in different conditioned spaces in real-time. Existing and commonly used ‘fixed’ schedules for HVAC systems are not sufficient and cannot adjust based on the dynamic changes in building environments. This study proposes a vision-based occupancy and equipment usage detection method based on deep learning for demand-driven control systems. A model based on region-based convolutional neural network (R-CNN) was developed, trained and deployed to a camera for real-time detection of occupancy activities and equipment usage. Experiments tests within a case study office room suggested an overall accuracy of 97.32% and 80.80%. In order to predict the energy savings that can be attained using the proposed approach, the case study building was simulated. The simulation results revealed that the heat gains could be over or under predicted when using static or fixed profiles. Based on the set conditions, the equipment and occupancy gains were 65.75% and 32.74% lower when using the deep learning approach. Overall, the study showed the capabilities of the proposed approach in detecting and recognising multiple occupants’ activities and equipment usage and providing an alternative to estimate the internal heat emissions.

Feasibility Study of a Supercritical Cycle as a Waste Heat Recovery System

2013 ◽  
Author(s):  
Antonio Agresta ◽  
Antonella Ingenito ◽  
Roberto Andriani ◽  
Fausto Gamma
Keyword(s):  
Power Systems ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Power Plants ◽  
Energy Savings ◽  
Waste Heat ◽  
Rankine Cycle ◽  
Waste Heat Recovery System ◽  
Recovery System ◽  
Organic Fluids

Following the increasing interest of aero-naval industry to design and build systems that might provide fuel and energy savings, this study wants to point out the possibility to produce an increase in the power output from the prime mover propulsion systems of aircrafts. The complexity of using steam heat recovery systems, as well as the lower expected cycle efficiencies, temperature limitations, toxicity, material compatibilities, and/or costs of organic fluids in Rankine cycle power systems, precludes their consideration as a solution to power improvement for this application in turboprop engines. The power improvement system must also comply with the space constraints inherent with onboard power plants, as well as the interest to be economical with respect to the cost of the power recovery system compared to the fuel that can be saved per flight exercise. A waste heat recovery application of the CO2 supercritical cycle will culminate in the sizing of the major components.

A Novel Flue Gas Heat Recovery System Integrated With Air Preheating in a Utility Boiler

2013 ◽  
Author(s):  
Cheng Xu ◽  
Gang Xu ◽  
Luyao Zhou ◽  
Yongping Yang ◽  
Yuanyuan Li ◽  
...  
Keyword(s):  
Flue Gas ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Power Plants ◽  
Energy Savings ◽  
Waste Heat ◽  
The Novel ◽  
Air Preheater ◽  
Recovery System ◽  
Condensed Water

Exhaust gas temperature in coal-fired power plants can reach approximately 120 °C to 140 °C, with the thermal energy accounting for approximately 3% to 8% of the total input energy. Therefore, the heat recovery of exhaust flue gas can improve the thermal efficiency of coal-fired power plants. Currently, the waste heat of flue gas can be recovered by installing an extra heat exchanger, also called low-temperature economizer (LTE), at the end of the boiler flue to heat a part of the condensed water. Extra work can then be obtained by saving the extracted steam and using it to heat the condensed water. However, the temperature of exhaust flue gas is only about 130 °C, which causes the flue gas to heat only the condensed water in the #7 and #8 regenerative heaters. Thus, the energy savings are inconspicuous. This paper proposes a novel flue gas heat recovery system to dramatically increase the temperature of flue gas in the LTE by comprehensive optimization of the air preheater and the LTE. A low-temperature (LT) air preheater can be installed after the LTE in the novel system so that the flue gas can be divided into two parts to heat the air. Simultaneously, the LTE can be installed between the two air preheaters, causing the temperature of flue gas in the LTE to reach above 170 °C. Hence, the temperature of condensed water in the LTE can be increased significantly. In addition, the LTE can replace the high-pressure extracted steam from the turbine, resulting in better energy savings. We also conduct case studies based on a typical 1,000 MW supercritical power generation unit in China. The results indicate better performance of the novel system, with a decrease in exergy loss and improvement in heat transfer characteristics. The reduction in standard coal equivalent of the novel system can reach 3.31g/kWh, nearly 2.4 times that of the system that uses conventional waste heat recovery. Our achievements provide a promising waste heat recovery methods of the utility boiler flue gas.

An adaptive MPC scheme for energy-efficient control of building HVAC systems

2021 ◽  
pp. 1-12
Author(s):  
Tingting Zeng ◽  
Dr. Prabir Barooah
Keyword(s):  
Energy Use ◽  
Energy Savings ◽  
Internal Heat ◽  
Hvac Systems ◽  
Planning Problem ◽  
Identification Algorithm ◽  
Periodic Model ◽  
Term Energy ◽  
Convergent Method

Abstract An autonomous adaptive MPC architecture is presented for control of heating, ventilation and air condition (HVAC) systems to maintain indoor temperature while reducing energy use. Although equipment use and occupant changes with time, existing MPC methods are not capable of automatically relearning models and computing control decisions reliably for extended periods without intervention from a human expert. We seek to address this weakness. Two major features are embedded in the proposed architecture to enable autonomy: (i) a system identification algorithm from our prior work that periodically re-learns building dynamics and unmeasured internal heat loads from data without requiring re-tuning by experts. The estimated model is guaranteed to be stable and has desirable physical properties irrespective of the data; (ii) an MPC planner with a convex approximation of the original nonconvex problem. The planner uses a descent and convergent method, with the underlying optimization problem being feasible and convex. A year long simulation with a realistic plant shows that both of the features of the proposed architecture - periodic model and disturbance update and convexification of the planning problem - are essential to get performance improvement over a commonly used baseline controller. Without these features, long-term energy savings from MPC can be small while with them, the savings from MPC become substantial.

LAHU Heat Recovery System Optimal Operation and Control Schedules

2005 ◽  
Vol 128 (3) ◽  
pp. 360-366 ◽  
Author(s):  
Yujie Cui ◽  
Mingsheng Liu
Keyword(s):  
Thermal Energy ◽  
Heat Recovery ◽  
Energy Savings ◽  
Pump Energy ◽  
Weather Conditions ◽  
Optimal Operation ◽  
Air Handling Unit ◽  
Recovery System ◽  
Heat Recovery System ◽  
And Control

Optimal operation and control of heat recovery in an integrated Laboratory Air Handling Unit (LAHU) system differs substantially from that in conventional dedicated AHUs for laboratory buildings with a 100% outside air AHU for laboratory spaces, since the LAHU allows economizer operation for both offices and laboratories. Optimal operation and control schedules of the heat recovery systems in the LAHU have been developed to minimize the total thermal energy cost. This paper presents the procedure, methodology, and results of generic optimal heat recovery control schedules for the LAHU and investigates its impact on the LAHU potential thermal and pump energy savings. The optimal control schedule can potentially save 14% to 27% thermal energy and 17% to 100% pump energy during the winter under weather conditions that prevail in Omaha, Nebraska. The findings discussed in this paper also apply to any heat recovery system, where AHU has an economizer function.

Analysis of Energy and Exergy of an Annealing Furnace

2011 ◽  
Vol 110-116 ◽  
pp. 2156-2162 ◽  
Author(s):  
Md. Hasanuzzaman ◽  
R. Saidur ◽  
N.A. Rahim
Keyword(s):  
Flue Gas ◽  
Heat Recovery ◽  
Energy Savings ◽  
Cost Benefit ◽  
Exergy Efficiency ◽  
Exergy Destruction ◽  
Annealing Furnace ◽  
Energy And Exergy ◽  
Recovery System ◽  
Exergy Losses

Furnace is the most common and important part in metal industries. The useful concept of energy and exergy utilization is analyzed to investigate the energy and exergy efficiency, exergy losses, energy savings and cost benefit of an annealing furnace. The exergy efficiency of the combustor is found to be 47.05 %. The energy and exergy efficiencies of the annealing chamber are found to be 17.74 % and 12.86 % respectively. The overall energy and exergy efficiencies of the furnace are found to be 16.86 % and 7.30 % respectively. The annealing chamber is the major contributor for exergy destruction about 57 % of the annealing furnace. By using a heat recovery system from flue gas, about 8.11% of fuel can be saved within the payback period of less than 2 months.

Solid Phase Heat Recovery and Multi Chamber Reduction for Redox Cycles

2014 ◽  
Author(s):  
Stefan Brendelberger ◽  
Jan Felinks ◽  
Martin Roeb ◽  
Christian Sattler
Keyword(s):  
Heat Recovery ◽  
Energy Savings ◽  
Solid Phase ◽  
High Heat ◽  
Special Focus ◽  
Chamber System ◽  
Complex Flow ◽  
Redox Cycles ◽  
Recovery System ◽  
Heat Recovery System

A system approach was used for the development of a new process concept for solar driven thermochemical redox cycles. Two aspects of this concept will be presented here. Since a high heat recovery rate for cycles using non-stoichiometric reduction has been identified as elementary in order to reach meaningful overall process efficiencies, a special focus was directed on this aspect. A quasi-countercurrent heat recovery system, which makes use of a particulate heat transfer medium, was outlined and numerically analyzed. The analysis shows that recovery rates of more than 70% seem realistic. Even though the heat recovery system is based on an arrangement of stages including relative complex flow pattern the basic principle seems promising and opens up new pathways for system design and optimization. The second aspect highlighted of the developed process concept is the use of a multi chamber system with optimized reaction conditions for the reduction of the redox material. By optimizing the pressure in a multi chamber system energy savings related to the pumping work of more than 20% are predicted. Also the execution of pre-reduction in the heat recovery system is discussed.

scholarly journals Primary energy efficiency assessment of a coil heat recovery system within the air handling unit of an operating room

2021 ◽  
Vol 2069 (1) ◽  
pp. 012113
Author(s):  
F J Rey-Martínez ◽  
J F San José-Alonso ◽  
E Velasco-Gómez ◽  
A Tejero-González ◽  
P M Esquivias
Keyword(s):  
Energy Consumption ◽  
Energy Balance ◽  
Thermal Energy ◽  
Heat Recovery ◽  
Energy Savings ◽  
Electric Energy ◽  
Primary Energy ◽  
Recovery System ◽  
Heat Recovery System ◽  
Coil Heat

Abstract Heat recovery systems installed in Air Handling Units (AHUs) are energy efficient solutions during disparate outdoor-to-indoor temperatures. However, they may be detrimental in terms of a primary energy balance when these temperatures get closer, due to the decrease in the thermal energy recovered compared to the global energy consumption required for their operation. AHUs in surgical areas have certain particularities such as their continuous operation throughout the year, the large airflows supplied and the strict exigencies on the supply air quality, avoiding any cross contamination. This work presents the measurements and analysis performed on a coil heat recovery (run-around) loop system installed in the AHU that serves a mixed-air ventilation operating room in a Hospital Complex. A primary energy balance is studied, including the thermal and electric energy savings achieved, considering the electric energy consumption by the recirculation pump and the additional power requirements of fans due to the pressure drop introduced. The obtained value is then used to predict the thermal energy savings achieved by the heat recovery system. Results are extrapolated to the Typical Meteorological Year to provide an order of magnitude of the primary energy and CO2 emissions saved through the operation of the coil heat recovery system.

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