A general methodology for optimal load management with distributed renewable energy generation and storage in residential housing

In the US, buildings represent around 40% of the primary energy consumption and 74% of the electrical energy consumption [U.S. Department of Energy (DOE). 2012. 2011 Buildings Energy Data Book. Energy Efficiency & Renewable Energy]. Incentives to promote the installation of on-site renewable energy sources have emerged in different states, including net metering programmes. The fast spread of such distributed power generation represents additional challenges for the management of the electricity grid and has led to increased interest in smart control of building loads and demand response programmes. This paper presents a general methodology for assessing opportunities associated with optimal load management in response to evolving utility incentives for residential buildings that employ renewable energy sources and energy storage. An optimal control problem is formulated for manipulating thermostatically controlled domestic loads and energy storage in response to the availability of renewable energy generation and utility net metering incentives. The methodology is demonstrated for a typical American house built in the 1990s and equipped with a single-speed air-to-air heat pump, an electric water heater and photovoltaic (PV) collectors. The additional potential associated with utilizing electrical batteries is also considered. Load matching performance for on-site renewable energy generation is characterized in terms of percentage of the electricity production consumed on-site and the proportion of the demand covered. For the purpose of assessing potential, simulations were performed assuming perfect predictions of the electrical load profiles. The method also allows determination of the optimal size of PV systems for a given net metering programme. Results of the case study showed significant benefits associated with control optimization including an increase of load matching between 3% and 28%, with the improvement dependent on the net metering tariff and available storage capacity. The estimated cost savings for the consumer ranged from 6.4% to 27.5% compared to no optimization with a unitary buy-back ratio, depending on the available storage capacity. Related reduction in CO₂ emissions were between 11% and 46%. Optimal load management of the home thermal systems allowed an increase in the optimal size of the PV system in the range of 13–21%.     

基于DPSSHP的分布式供能系统在赣南地区的研究

赣南地区城市污水排放量较大,工业废水富含大量余热。发展基于直接式原生污水源热泵(Direct Primary Sewage Source Heat Pump,简称DPSSHP)的分布式供能系统,向建筑供冷供热,将大大降低建筑空调采暖能耗。根据赣南地区实际情况,提出了DPSSHP系统针对不同类型建筑的应用规划。选取了地下水源热泵,大型螺杆式冷水机组+燃煤锅炉,风冷式空气源热泵、DPSSHP,从系统初投资、运行费用、单位面积运行成本等方面进行经济性比较,得出DPSSHP较为经济。     

基于ANN的绿色办公建筑HVAC系统运行能耗预测

办公建筑中暖通空调系统(HVAC系统)的运行能耗占总能耗比例较高。随着绿色建筑的大力推广,准确预测绿色办公建筑HVAC系统能耗是建筑运行优化的关键。研究以天津市某绿色办公建筑为研究对象,根据绿色办公建筑G中的HVAC系统——地源热泵系统和空调通风系统能耗的实际监测数据,建立了基于人工神经网络的能耗预测模型。研究结果表明,建立的分类多层感知器神经网络预测模型预测精度最好,仅基于气象参数及时间能够精确的预测建筑HVAC系统的小时能耗,为我国绿色办公建筑的设计和运行优化提供科学支持。     

Generalizable occupant-driven optimization model fordomestic hot water production in NZEB

The primary objective of this paper is to demonstrate improved energy efficiency for domestic hot water(DHW)production in residential buildings.This is done by deriving data-driven optimal heating schedules(used interchangeably with policies)automatically.The optimization leverages actively learnt occupant behaviour and models for thermodynamics of the storage vessel to operate the heating mechanism-an air-source heat pump(ASHP)in this case-at the highest possible efficiency.The proposed algorithm,while tested on an ASHP,is essentially decoupled from the heating mechanism making it sufficiently robust to generalize to other types of heating mechanisms as well.Simulation results for this optimization based on data from 46 Net-Zero Energy Buildings(NZEB)in the Netherlands are presented.These show a reduction of energy consumption for DHW by 20%using a computationally inexpensive heuristic approach,and 27%when using a more intensive hybrid ant colony optimization based method.The energy savings are strongly dependent on occupant comfort level.This is demonstrated in real-world settings for a low-consumption house where active control was performed using heuristics for 3.5months and resulted in energy savings of 27%(61 kW h).It is straightforward to extend the same models to perform automatic demand side management(ADSM)by treating the DHW vessel as a flexibility bearing device.     

Energy savings potential of a desiccant assisted hybrid air source heat pump system for residential building in hot summer and cold winter zone in China

In hot summer and cold winter zone in China, air conditioning system has four running modes yearly including cooling with dehumidification, cooling, dehumidification and heating in residential buildings. The conventional air source heat pump (ASHP) system is not designed to independently control temperature and humidity, and is not very suitable for the dehumidification mode in the view of building energy consumption. A novel ASHP system combining radiant cooling/heating for residential buildings was presented. The main feature of this hybrid ASHP system is that desiccant wheel and cooling coil accomplish dehumidification process together, and the regenerative heat needed by the desiccant wheel is supplied by the condenser dissipated heat. Based on simulation studies and performance analysis, this paper predicts the primary energy consumption of the hybrid ASHP system in comparison with the conventional ASHP system during the cooling and heating seasons. It was found that primary energy requirement can be reduced by more than 8% in cooling with dehumidification mode, by 50% in dehumidification mode, and by more than 14% in heating mode. The study results prove that the hybrid ASHP system can keep great energy saving and running cost saving yearly, especially in the dehumidification process.     

Modeling and economic analysis of gas engine heat pumps for residential and commercial buildings in various climate regions of Iran

There is an increasing trend in using heat pumps in air conditioning (heating/cooling) systems of residential and commercial buildings. The required power to drive the compressor of vapor compression heat pump cycles may be provided by either an electrical motor or an internal combustion engine. In this paper thermal modeling and economic analysis of gas engine heat pumps (GEHPs) are presented based on energy and mass balance equations as well as the gas engine operating parameters (such as thermal efficiency, fuel consumption and fuel mass flow rate) and heat pump operating parameters (such as evaporator and condenser capacity and compressor input power). Based on the modeling results and with estimating GEHP fuel consumption, the economic analysis of using gas engine heat pumps (in comparison with the electrical heat pumps) at various climate regions of Iran, for both residential and commercial (office) buildings, and for both cooling and heating modes, was performed. Appropriate cost functions for predicting GEHP capital investment were proposed. Three approaches including equivalent uniform annual cost (EUAC), the annual cost of energy consumption, and payback period were applied in the economic analysis.     

Application of model based predictive control for water-based floor heating in low energy residential buildings

A model based predictive control method is applied in order to determine the optimal supply fluid temperature in the case of concrete embedded water-based floor heating in low energy residential buildings. The aim of the control is to keep the indoor temperature within a defined comfort interval. The forthcoming supply fluid temperature is obtained through a numerical optimisation based on a prediction of the upcoming heat demand. The elementary response function, which is the basis for the method, is obtained from a numerical control volume model, and as an alternative, from a simplified 2-node lumped model. The accuracy of the results obtained from the simplified model is surprisingly good in comparison to the detailed numerical model. The control method is applied for a single room for which a perfect prognosis of the heat demand exists. The results show a fairly steady optimised supply fluid temperature.     

空气源热泵热水机组在游泳池水加热中的应用

以某文体活动中心为例,从耗热量计算、空气源热泵的选型、空气源热泵的能耗计算三方面阐述了空气源热泵技术在游泳池水加热中的应用,并将其与燃油锅炉的能耗费用进行了比较,以说明空气源热泵技术的优越性。     

Modelling and simulation of a heat pump for simultaneous heating and cooling

The heat pump for simultaneous heating and cooling (HPS) carries out space heating, space cooling and hot water production for small office and residential buildings. It works under heating, cooling and simultaneous modes to produce hot and chilled water according to the thermal demand of the building. A subcooler connected to a water tank is placed after the condenser to recover some energy by subcooling of the refrigerant during a heating mode. The water loop at a higher temperature than ambient air is used subsequently as a source for a water evaporator. Average winter performance is improved compared to a standard reversible heat pump (HP). The air evaporator is defrosted by a two-phase thermosiphon without stopping the heat production. The operation of the HPS is modelled using TRNSYS software. The model is validated using results of an experimental study carried out on a HPS prototype working with R407C. Annual simulations of the HPS coupled to a hotel are run in order to evaluate annual performance and energy consumption of the system. The results are compared to the ones of a standard reversible HP. Depending on the scenario, savings in electric energy consumption and annual performance improvement can reach respectively 55% and 19%.     

Renewable energy options for buildings: Case studies

This paper deals with a novel approach to study renewable energy options for buildings to make them more efficient, more cost effective, more environmentally benign, and more technologically attractive. To demonstrate the application of this study, four buildings are chosen as case studies with two from the residential sector, one commercial/institutional building, and one industrial building. A ground source heat pump for heating and cooling, a solar water heater for space heating and/or hot water, and a photovoltaic panel to generate electricity are designed for these case studies. Attempt is made to design projects under hybrid systems combined from two technologies are developed for the above-mentioned four cases. Results obtained indicate that solar thermal option for hot water and space heating becomes the most cost effective one for all cases (e.g., $4956 for Cases 1 and 2 and $70,652 for Case 3, and $91,361 for Case 4). In addition, solar electricity through PVs is technologically the most suitable one to meet the electricity demand. The ground source heat pump option is quite attractive from the efficiency and environmental impact point of views although it requires installation and maintenance, etc. Finally, hybrid systems provide better advantages, such as higher efficiency, reduced cost, reduced emissions, etc.     

地源热泵与蓄热式电锅炉冬季制热的节能性实测与分析

地源热泵作为一种节能环保的新型冷热源,越来越受到关注,并逐步推广应用.针对夏热冬冷地区冬季上海市某建筑,利用土壤源热泵加干盘管联合制热对办公用房进行供暖,且在相同制热量的情况下对比蓄热电锅炉系统,对两种能耗进行分析,发现在考虑初投资的情况下,地源热泵比蓄热式电热锅炉节能约35.1％.     

Optimisation of a heat pump space heating system

Because the heat pump has a very high capital cost compared with other forms of space heating, and also because the peak space heating demand in the U.K. only occurs for a few hours in the year, it has become recognised practice to install low capital cost supplementary electric heating to meet peak demands. A technique is described which optimizes the mix of heat pump and supplementary capacity to minimize the total cost of operation. A simulation model is employed which uses a weather tape containing hourly outside air temperatures to generate a space heating demand profile for a building of known thermal characteristics. The technique specifically allows the examination of intermittent heating, and in this paper is applied to a small factory operating on a variety of shift patterns. This application is of particular interest because it considers the effect of maximum demand charges on the economics of heat pump space heating systems. It is concluded that the optimum heat pump capacity depends strongly upon the length of shift, and that optimum oversizing of the heat pump system for intermittent heating appears to be lower than for conventional heating systems as a result of maximum demand pricing.     

Energy consumption and potential energy savings in old school buildings

Energy and indoor environmental audits of energy consumption and indoor air quality were taken in 24 school buildings in Slovenia. The audits show that these buildings are high energy consumers and have poor indoor air quality, as expressed by 60% of the surveyed pupils. This article deals with energy consumption in the analysed schools. The nominal heating power of boilers, and heat exchangers, which are used in district heating, show a 57% overcapacity. The heat losses of the school buildings are 89% higher than the recommended values. According to our analysis of the possible measures to improve the situation in the school buildings, it will not be possible to ensure rational energy use and good indoor air quality with low investment costs. Should we change from hot-water heating systems and natural ventilation to energy efficient blown air systems with which one device provides the comfort of both heating and air conditioning?     

杭州绿色公共建筑应用可再生能源方案比较

从可再生能源技术特点出发,结合公共建筑用能特征,分析了杭州地区绿色公建中采用太阳能热水、太阳能光伏和土壤源热泵系统三种可再生能源的可行性,为公共建筑可再生能源方案选择提供指导。     

Calculation of the yearly energy performance of heating systems based on the European Building Energy Directive and related CEN standards

According to the Energy Performance of Buildings Directive (EPBD) all new European buildings (residential, commercial, industrial, etc.) must since 2006 have an energy declaration based on the calculated energy performance of the building, including heating, ventilating, cooling and lighting systems. This energy declaration must refer to the primary energy or CO₂ emissions.The European Organization for Standardization (CEN) has prepared a series of standards for energy performance calculations for buildings and systems. This paper presents related standards for heating systems. The relevant CEN-standards are presented and a sample calculation of energy performance is made for a small single family house, an office building and an industrial building in three different geographical locations: Stockholm, Brussels, and Venice.The additional heat losses from heating systems can be 10-20% of the building energy demand. The additional loss depends on the type of heat emitter, type of control, pump and boiler.     

地源热泵技术对建筑节能的重要意义

随着科学技术的进步、人们对生活质量要求的不断提高,各类商用建筑、住宅的室内温度达到冬暖夏凉已成为最普遍的要求。在传统的供热系统中,燃煤锅炉是最常见的设备,然而随着煤炭价格的居高不下,环保观念日益深入民心,这种设备已经面临着淘汰的命运。地源热泵技术作为一种新型的空调系统,不仅对建筑节能具有重大意义,而且对环境保护有着巨大的影响。简单介绍了地源热泵技术的概念和原理,以及这种技术目前在国内外的应用情况,详细分析了地源热泵技术对建筑节能的重要意义。     

An aquifer thermal storage system in a Belgian hospital: Long-term experimental evaluation of energy and cost savings

Over a three years period, an aquifer thermal energy storage system was monitored in combination with a heat pump for heating and cooling of the ventilation air in a Belgian hospital. The installation was one of the first and largest ground source heat pump systems in Belgium. Groundwater flows and temperatures were monitored as well as the energy flows of the heat pumps and the energy demand of the building. The resulting energy balance of the building showed that the primary energy consumption of the heat pump system is 71% lower in comparison with a reference installation based on common gas-fired boilers and water cooling machines. This corresponds to a CO₂-reduction of 1280 ton over the whole measuring period. The overall seasonal performance factor (SPF) for heating was 5.9 while the ATES system delivered cooling at an efficiency factor of 26.1. Furthermore, the economic analysis showed an annual cost reduction of k€ 54 as compared to the reference installation, resulting in a simple payback time of 8.4 years, excluding subsidies.     

热计量对燃气集中供暖用气规律及储气的影响

分析了住宅建筑、公共建筑热计量前后的小时耗热量变化规律和供暖用气的供需平衡,对比了热计量前、住宅建筑热计量后、公共建筑热计量后、住宅建筑用户占60％和公共建筑用户占40％的综合区域热计量后所需的储气容积.热计量实施后,需要更大的储气容积来平衡集中供暖小时用气的不均匀性.     

空气源热泵在建筑节能中大有作为

通过对空调、采暖、生活热水的需求性分析,指出空气源热泵在运用了热回收、数码涡旋等技术后,其节能、环保和经济性能有了显著的改善,不仅可广泛用于长江流域,即使在我国寒冷地区也具备了应用这种先进的节能技术和设备的可能性.空气源热泵在建筑节能中完全是可以大有作为的.建议适宜地区的各级政府积极宣传、推广、应用空气源热泵,促进我国的节能减排目标早日实现.     

Case studies of energy consumption in residential buildings in Russia's middle belt area

This paper describes the analytical results of heating energy consumption monitoring and the determination of heat protection levels for both single-family and multi-family buildings in Russia. Experiments have been jointly conducted by Russian and American researchers from the Research Institute for Building Physics, Gosstroy of Russia, and the Natural Resources Defense Council. The paper describes qualimetric methods which provide a quantitative estimation of thermal and energy performance by using instrumental facilities and non-destructive methods.

The first Section gives a brief methodological summary for determining on-site building energy and thermal performance. The second part reviews the field results of energy monitoring to determine techniques that may result in the highest energy conservation effect for standard single-family houses in Russia. The third Section presents a comparative energy analysis of the use of highly insulating windows in a multi-family apartment building in field conditions. The experiments conducted prove that it is possible to ensure a 20–25% reduction in energy consumption for residential buildings under actual conditions existing in Russia. Finally, a methodology for assessing whole-building energy consumption for multi-family buildings is described.