A Study of Predictive Control Strategies for Optimally Designed Solar Homes

This thesis investigates the development of predictive control strategies for optimally or near-optimally designed solar homes. Optimal design refers to the integration of renewable energy technologies (mainly active and passive solar) with a high-quality building envelope as well as efficiency and conservation measures to achieve substantial reductions in energy consumption and peak demand. Effective implementation of these technologies requires an integrated design approach, which considers their interactions with the building and its services. Furthermore, control strategies must be an essential part of the integrated design of a building to improve energy performance and ensure occupant comfort. In optimally designed solar homes, control strategies should incorporate the collection, storage and delivery of solar energy. Weather forecasts along with an understanding of the building’s thermal dynamics (e.g., time delays due to thermal mass) enable predicting and managing loads and solar energy availability. Design and operation strategies of a case study, the Alstonvale House, are presented. Features of this house include passive solar design, a building-integrated photovoltaic/thermal (BIPV/T) system coupled with a solar-assisted heat pump, a thermal energy storage tank and a radiant floor heating system in a thermally massive concrete slab. Design and control approaches developed for the Alstonvale House provided the basis for generalized control strategies applicable to optimally designed solar homes. Simplified building models, which can be derived from more detailed models or on-site measurements, can facilitate the implementation of predictive control techniques. In this investigation, model-based predictive control was applied to a radiant floor heating system and the position of roller blinds in a room with high solar gains. Predictive control can also be applied to optimize the operation of renewable energy systems. In this study, forecasts of heating loads and solar radiation were used in a dynamic programming algorithm to select a near-optimal set-point trajectory for an energy storage tank heated with a heat pump assisted by a BIPV/T system

Load Matching and Grid Interaction of Net Zero Energy Buildings

“Net Zero Energy Building” has become a prominent wording to describe the synergy of energy efficient building and renewable energy utilization to reach a balanced energy budget over a yearly cycle. Taking into account the energy exchange with a grid infrastructure overcomes the limitations of seasonal energy storage on-site. Even though the wording “Net Zero Energy Building” focuses on the annual energy balance, large differences may occur between solution sets in the amount of grid interaction needed to reach the goal. The paper reports on the analysis of example buildings concerning the load matching and grid interaction. Indices to describe both issues are proposed and foreseen as part of a harmonized definition framework. The work is part of subtask A of the IEA SHCP Task40/ECBCS Annex 52: “Towards Net Zero Energy Solar Buildings”

Time-mean wall static pressure distributions and module friction factors for spatially periodic fully developed flows in interrupted-plate rectangular ducts

An experimental study of spatially periodic fully developed flows of air in straight rectangular ducts with interrupted-plate inserts is presented. These flows have features similar to those produced in plate-fin passages of compact heat exchanger cores. The formulation of mathematical models and numerical solution methods for the prediction of these flows continues to be a challenging and largely unattained goal. The main goal of this work is to contribute experimental results suitable for testing and refining such models and solution methods. Airflows in nine different interrupted-plate rectangular ducts were considered. Reynolds numbers considered (based on Kays and London's definition of hydraulic diameter and the maximum average streamwise velocity) ranged from about 2,000 to 65,000. Time-mean static pressure distributions along the axial centreline of the top wall of the ducts, and module friction factor versus Reynolds number data, all in the spatially periodic fully developed region, were obtained

Mínimos de detección para la prueba de Scott y Duquenois Levinne

35 p

A Methodology for the Enhancement of the Energy Flexibility and Contingency Response of a Building through Predictive Control of Passive and Active Storage

Optimal management of thermal energy storage in a building is essential to provide predictable energy flexibility to a smart grid. Active technologies such as Electric Thermal Storage (ETS) can assist in building heating load management and can complement the building’s passive thermal storage capacity. The presented paper outlines a methodology that utilizes the concept of Building Energy Flexibility Index (BEFI) and shows that implementing Model Predictive Control (MPC) with dedicated thermal storage can provide predictable energy flexibility to the grid during critical times. When the utility notifies the customer 12 h before a Demand Response (DR) event, a BEFI up to 65 kW (100% reduction) can be achieved. A dynamic rate structure as the objective function is shown to be successful in reducing the peak demand, while a greater reduction in energy consumption in a 24-hour period is seen with a rate structure with a demand charge. Contingency reserve participation was also studied and strategies included reducing the zone temperature setpoint by 2∘C for 3 h or using the stored thermal energy by discharging the device for 3 h. Favourable results were found for both options, where a BEFI of up to 47 kW (96%) is achieved. The proposed methodology for modeling and evaluation of control strategies is suitable for other similar convectively conditioned buildings equipped with active and passive storage

A Methodology for the Enhancement of the Energy Flexibility and Contingency Response of a Building through Predictive Control of Passive and Active Storage

Optimal management of thermal energy storage in a building is essential to provide predictable energy flexibility to a smart grid. Active technologies such as Electric Thermal Storage (ETS) can assist in building heating load management and can complement the building’s passive thermal storage capacity. The presented paper outlines a methodology that utilizes the concept of Building Energy Flexibility Index (BEFI) and shows that implementing Model Predictive Control (MPC) with dedicated thermal storage can provide predictable energy flexibility to the grid during critical times. When the utility notifies the customer 12 h before a Demand Response (DR) event, a BEFI up to 65 kW (100% reduction) can be achieved. A dynamic rate structure as the objective function is shown to be successful in reducing the peak demand, while a greater reduction in energy consumption in a 24-hour period is seen with a rate structure with a demand charge. Contingency reserve participation was also studied and strategies included reducing the zone temperature setpoint by 2∘C for 3 h or using the stored thermal energy by discharging the device for 3 h. Favourable results were found for both options, where a BEFI of up to 47 kW (96%) is achieved. The proposed methodology for modeling and evaluation of control strategies is suitable for other similar convectively conditioned buildings equipped with active and passive storage

Simulation and performance analysis of an active PCM-heat exchanger intended for building operation optimization

This paper presents a simulation study of an active energy storage device intended to enhance building operation. This device –which is designed for installation in the ceiling plenum of an office, a mechanical room or in other convenient locations– consists of an arrangement of several panels of a phase-change material. It may be charged or discharged as required with an air stream passing between the panels, thus operating as a PCM-air heat exchanger (PCM-HX). The first part of the paper focuses on the design of the PCM-HX. Several design configurations are evaluated; investigated parameters include the PCM-HX dimensions, the number of air channels and airflow rates. The paper also includes an experimental validation of the PCM model. Performance criteria that were considered in the parametric study include the amount of stored heat, the time needed to charge/discharge the PCM storage and the overall energy density of the device. The second part of the paper evaluates different control strategies aimed at reducing peak demand and the size of HVAC system. The impact on peak load of a linear ramp for the temperature setpoint is investigated: it was found that a two hour linear ramp in temperature setpoint –together with a PCM-HX configuration with six air channels– can reduce the peak heating load by 41% as compared to a benchmark case without the PCM-HX

Transient and steady state models for open-loop air-based BIPV/T systems

Open-loop building-integrated photovoltaic/thermal (BIPV/T) systems with air as the heat transfer fluid can supply a substantial portion of the space heating and hot water needs of residential and commercial buildings in cold climates. Over the last few years, several customized mathematical models for these systems have been developed. This paper presents a more general model useful for design or control purposes which allows for steady-state or transient analysis. Steady state models provide a quick evaluation of the energy balance and system performance useful for design. Transient models provide more insight valuable for development of control algorithms and system desig