Enhancement of the UK Standard Assessment Procedure (SAP) solar water heating prediction algorithm using parametric dynamical thermal simulations

SAP is the UK Government’s method for calculation of a dwelling’s energy efficiency and carbon dioxide emissions. This paper presents a method of informing the SAP procedure regarding evaluation of the advantage given to SAP ratings by installation of typical domestic Solar Domestic Hot Water (SDHW) systems. Comparable SDHW systems were simulated using the dynamic thermal simulation package TRNSYS and results were translated into empirical relations in a form that could be input into the SAP calculation procedure. Findings were compared against the current SAP algorithm and differences explained. Results suggest that calculation variances can exist between the SAP methodology and detailed dynamic thermal simulation methods. This is especially true for higher performance systems that can deviate greatly from default efficiency parameters. This might be due to SAP algorithms being historically based on older systems that have lower efficiencies. An enhancement to the existing SAP algorithm is suggested

Complex energy simlulation using simplified user interaction mechanisms

Simulation of energy systems and associated thermodynamic domains is very powerful in delivering precise information at high resolution. Modelling software requires detailed information about the energy system. The specialised user usually has questions about specific aspects of the energy system and may not be interested in the complete set of outputs available from simulation results. Similarly the specialised user may only be concerned about a subset of the inputs provided to the software. This suggests an opportunity to develop an input / output scheme tailored for the specialised user. The power of simulation can be accessed through the use of simplified interfaces. Although these restrict flexibility in terms of model input / output data the specialised user is only interested in a subset of the capability of the underlying simulation tool. Robust results rely on a consistent underlying simulation context, this restricted interface ensures that only the parameters of interest to the users are modifiable and that other simulation parameters remain fixed ensuring a consistent and repeatable output. One such example of limited user interaction for both output and input is the ADEPT interface to whole building and plant dynamic modelling and simulation suite ESP­r (ESRU 2002). The interface was developed in the context of the UK domesticheating market. This paper describes the development of the ADEPT tool and associated spreadsheet templates in order to provide a readily usable platform for the study of domestic heating systems and controls for plant and control components manufacturers, regulatory authorities and research organisations

The effect of hot water use patterns on heating load and demand shifting opportunities

Heating loads for modern houses are lower than older houses with a larger proportion used to service domestic hot water (DHW). Electric heating systems, e.g. air source heat pumps (ASHP) and underfloor heating, offer load shifting possibilities with solar thermal DHW systems providing further opportunities. Other dynamic effects such as heat loss from water tank and stochastic demand need to be considered too. Hence integrated dynamic simulation is adopted to look at building thermal interactions with explicit plant representation and linked network mass flow and power flow solutions. Stochastic DHW use patterns characteristic of the UK are investigated. Different time controlled heating profiles are simulated to investigate demand shifting. Findings show user behaviour strongly influences water heating requirements, solar DHW system effectiveness and consequentially load shifting potential

Development and validation of detailed building, plant and controller modelling to demonstrate interactive behaviour of system components

As plant modelling becomes capable of more complexity and detailed resolution, new opportunities arise for the virtual evaluation of discrete plant components such as flow control and energy conversion devices, and controllers. Such objects are conventionally developed and tested at the prototype stage in a laboratory environment. Designers now seek to use modelling technology to extend their understanding from limited laboratory test results to full building and plant system analysis. This paper describes the development of a modelling system, using ESP-r, for typical United Kingdom domestic house types with hydronic gas or oil fired central heating including radiator and underfloor heating systems, and with a variety of conventional or advanced control types. It demonstrates the ability of detailed building and plant modelling to reveal unexpected insights into how real control systems perform in combination with other plant items and in different building types, including estimation of their influence on annual energy consumption. Comparisons with measurements taken in test rooms confirm that the observed behaviour of controls is realised in practice. The authors conclude that the complex dynamic interactions that take place between the various elements that make up a real building energy system have an important influence on its overall energy performance, revealing causes of variance that cannot be identified by laboratory testing alone, or by simplistic energy assessment tools

Predicting the effect of changes to the urban environment on future electrical demand using building simulation and archetype models

Future urban electrical loads are of interest to a range of stakeholders from utilities to network planners. In this paper, a pragmatic approach to the modelling of urban electrical demands using archetype models and simulated building demand profiles is described. The profiles can be scaled, transformed and combined to produce time-series electrical loads for multiple buildings connected to a substation in a distribution network. The modelling approach has been verified against measured demand data. Possible changes in future peak urban electrical demand were quantified for a sample of substations in Glasgow, UK, using four future demand scenarios. The picture emerging was complex, with peak demand increasing in some cases where electric vehicles and electrified heating combine. However, there were many situations where a combination of improved energy efficiency and microgeneration lead to reduced peak demand

Pervasive sensing as a mechanicsm for the effective control of CHP plant in commerical buildings

A recently completed, EPSRC-funded project researched the use of low cost, pervasive sensing to monitor building environmental conditions and occupant interactions as a means to reduce the uncertainties associated with the creation of a building model for refurbishment options and smarter control appraisal. This paper gives a brief introduction to the pervasive sensing system as established within the project and describes its use to enable simulations of the multi-input, multi-output (MIMO) control of a combined heat and power (CHP) unit in a commercial building context. Within the project, data from pervasive sensing was used to calibrate a simulation model of an office building and impose occupant-related inputs at the time step level as a means to reduce modelling uncertainty. The MIMO input parameters considered include space temperatures, heat store temperatures, electricity demand and electricity tariff, while the output parameters include space heat supply, heat stored, electricity utilised locally or exported, and CHP unit fuel use. The simulation model was used to compare performance when the CHP unit is subjected to conventional and MIMO control. It is demonstrated that the pervasive sensing approach enables control that delivers enhanced energy performance

Development of adaptive algorithms for the operation of windows, fans, and doors to predict thermal comfort and energy use in Pakistani buildings

This year-round field investigation of the use of building controls (windows, doors and fans) in 33 Pakistani offices and commercial buildings focuses on 1) how the occupants' behavior is related to thermal comfort, 2) how people modify the indoor environment and 3) how we can predict the occupants' behavior. We have found that the use of building controls depends on climate and season. The use of these controls has a cooling effect on the occupant through increasing the air movement or the ventilation. The behavioral model yields adaptive algorithms that can be applied in building thermal simulations to predict the effects of the occupants' behavior on energy-saving building design

Pervasive sensing as a mechanism for the effective control of CHP plant in commercial buildings

A recently completed, EPSRC-funded project researched the use of low cost, pervasive sensing to monitor building environmental conditions and occupant interactions as a means to reduce the uncertainties associated with the creation of a building model for refurbishment options and smarter control appraisal. This paper gives a brief introduction to the pervasive sensing system as established within the project and describes its use to enable simulations of the multi-input, multi-output (MIMO) control of a combined heat and power (CHP) unit in a commercial building context. Within the project, data from pervasive sensing was used to calibrate a simulation model of an office building and impose occupant-related inputs at the time step level as a means to reduce modelling uncertainty. The MIMO input parameters considered include space temperatures, heat store temperatures, electricity demand and electricity tariff, while the output parameters include space heat supply, heat stored, electricity utilised locally or exported, and CHP unit fuel use. The simulation model was used to compare performance when the CHP unit is subjected to conventional and MIMO control. It is demonstrated that the pervasive sensing approach enables control that delivers enhanced energy performance

Orchestration of renewable generation in low energy buildings and districts using energy storage and load shifting

There is increasing penetration of renewable generation in buildings and districts. There are challenges in making the effective use of this generation. The objective of the ORIGIN project (Orchestration of Renewable Integrated Generation In Neighborhoods) is to shape loads so that the fraction of energy consumed that is from local renewable generation is maximized, and energy imported from outside sources is minimized. This paper presents the overall approach taken in the ORIGIN project and explores building physics aspects of solar thermal storage system orchestration. The case study districts are briefly introduced and characteristics of their generation, buildings, districts and shiftable loads described. The orchestration approach taken in ORIGIN is then presented. At the core of the ORIGIN system is the orchestration algorithm which generates informational and control outputs to shape future loads to best meet the objectives. The model based approach used to quantify thermal and electrical load shifting opportunities for pre-charging, coasting or avoiding loads, while meeting thermal comfort and other demands, is described using a solar thermal storage system as an example. The future steps for the ORIGIN project; retrofit of the ORIGIN system into existing districts and potential for other future applications is briefly discussed

Considering the impact of situation-specific motivations and constraints in the design of naturally ventilated and hybrid buildings

A simple logical model of the interaction between a building and its occupants is presented based on the principle that if free to do so, people will adjust their posture, clothing or available building controls (windows, blinds, doors, fans, and thermostats) with the aim of achieving or restoring comfort and reducing discomfort. These adjustments are related to building design in two ways: first the freedom to adjust depends on the availability and ease-of-use of control options; second the use of controls affects building comfort and energy performance. Hence it is essential that these interactions are considered in the design process. The model captures occupant use of controls in response to thermal stimuli (too warm, too cold etc.) and non-thermal stimuli (e.g. desire for fresh air). The situation-specific motivations and constraints on control use are represented through trigger temperatures at which control actions occur, motivations are included as negative constraints and incorporated into a single constraint value describing the specifics of each situation. The values of constraints are quantified for a range of existing buildings in Europe and Pakistan. The integration of the model within a design flow is proposed and the impact of different levels of constraints demonstrated. It is proposed that to minimise energy use and maximise comfort in naturally ventilated and hybrid buildings the designer should take the following steps: 1. Provide unconstrained low energy adaptive control options where possible, 2. Avoid problems with indoor air quality which provide motivations for excessive ventilation rates, 3. Incorporate situation-specific adaptive behaviour of occupants in design simulations, 4. Analyse the robustness of designs against variations in patterns of use and climate, and 5. Incorporate appropriate comfort standards into the operational building controls (e.g. BEMS)