Chengchu Yan

Building power demand response methods toward smart grid

Smart grid has been drawing attention particularly when renewable generations are integrated. In order to ensure high power reliability and energy efficiency in an electrical grid, research and application has been conducted at power supply side to solve the grid critical issues: peak load and power imbalance. However, as the major end-users at power demand side, buildings can also play a significant and cost-effective role by making use of their power demand responses. Different demand response programs (e.g., time- and incentive-based) have been developed and applied for encouraging the end-users to change their energy usage behaviors expected by the grid. Generally, buildings are able to limit and/or shift the power demands according to their own considerations under the specific incentives. A comprehensive review on the building power demand response methods is still missing, although research and application has been investigated and conducted on power demand aspects concerning the building system configuration and the control strategies of power demand optimization. This article, therefore, presents a comprehensive review on the strategies, impacts, and benefits of building power demand response in a grid to systematically evaluate and make better use of their demand response potentials. The possibility of developing proper building power demand response strategies for offline and online applications of the smart grid is also discussed.

Robust optimal design of building cooling systems concerning uncertainties using mini-max regret theory

Various uncertainties exist in cooling systems at the plan and design stage. The conventional design method usually selects the cooling system or configurations without considering uncertainties, which may be risky because the performance of the cooling system may deviate from the expected, together with increased cost and reduced benefit due to uncertainties and variations in actual working conditions. A new, simple, and effective method is proposed to optimize the design of cooling systems and get the robust optimal cooling system by considering uncertainties in the information used at the design stage. The mini-max regret theory is used to realize the method. Two important problems in the design of cooling systems are studied: chiller combinations and chilled water pump configurations. By considering the uncertainties in the cooling load, the robust optimal chiller combination can be obtained. By considering the uncertainties in the resistance of chilled water pipelines, the robust optimal chilled water pump configuration can be determined.

Building demand response and control methods for smart grids: A review

Demand response provides a solution to the grid imbalance problems which restrict the use of renewable energy. Since buildings possess a high amount of flexible load, they could contribute to smart grid stability and achieve cost savings for buildings and the other participants in the smart grid. However, the research and application of building demand response are still at the beginning stage. Majority of the existing demand response studies are from the view point of the grid side, rather than the demand side. This article, therefore, provides an overview on the studies on building demand response from the view point of buildings at the demand side. It mainly consists of two parts: (1) an overview of different types of demand response programs, and the status of the demand response programs in several countries and regions; (2) a review on the control methods for demand response in commercial and residential buildings. This review intends to support the further development of demand response methods for future smart grid applications and their implementation in buildings.

Retrofitting building fire service water tanks as chilled water storage for power demand limiting

Peak demand cost usually contributes a large proportion of the total electricity bills in buildings. Using existing building facilities for power demand limiting has been verified as effective measures to reduce monthly peak demands and associated costs. Fire service water tanks exist in most commercial buildings. This paper presents a comprehensive study on how to effectively retrofit existing building fire service water tanks as chilled water storage for power demand limiting. Important technical and economic factors that may affect the implementation of the proposed retrofitting are addressed. Two retrofitting schemes, i.e. a small ΔT (storage temperature difference) scheme and a large ΔT scheme are proposed for integrating the chilled water storage system into an existing all-air system and an existing air-water air conditioning system, respectively. Two optimal demand limiting control strategies, i.e. time-based control and demand-based control, are proposed for maximizing the monthly peak demand reduction of buildings with regular and variable peak occurring time, respectively. The cost-effectiveness of different retrofitting schemes in three real buildings in Hong Kong is analysed. Results show that substantial cost savings can be achieved with short payback periods (0.7–2.6 years) for the retrofits in these three buildings. Practical application: This paper presents a techno-economic analysis on retrofitting existing building fire service water tanks as chilled water storage for power demand limiting and operational cost saving. The proposed retrofitting schemes and demand limiting control strategies enable chilled water storage systems to be readily applied to most existing buildings. Building owners can benefit from the peak demand cost saving as the monthly peak demand can be significantly reduced by using chilled water storage. The extra costs involved in tank retrofits and system integrations can be paid back within three years.