Inverse Dynamics based Energy Assessment and Simulation : IDEAS

The Standard Assessment Procedure (SAP) is the UK Government’s approved methodology for assessing the energy ratings of dwellings. SAP is a calculation method based upon empirical relations from measured data. A yearly calculation was used in SAP until the release of SAP 2009, which employs monthly calculations. SAP has moved from using a large time step with a coarse time resolution to a smaller time step with a medium time resolution. Rising CO2 emissions from dwellings advocate that properties designed in a sustainable method will become commonplace in the future. In tandem with enhanced sustainability, dwellings will increasingly be designed with implementations of renewable energy generation. The modelling of renewables in SAP has been highlighted as an area where SAP could benefit from additional research. Modelling future complex dwellings and systems will require an advanced calculation method which is capable of more detailed modelling and simulation; with a smaller time step which is measured in minutes and not months, producing results allowing more detailed analysis of energy performance. Dynamic Simulation Methods (DSMs) already exist which can operate at a very small time step. However with DSMs it is very difficult to make a comparison with SAP as the temperatures used in SAP are not well understood. To calculate energy consumption the SAP methodology guarantees that a standard occupancy temperature profile is met perfectly. A dynamic method which also guarantees the SAP standard occupancy temperature profile is required. This is difficult in complex DSMs as their control algorithms are often inadequate to optimise the heating system to guarantee that a temperature is met perfectly. The contribution to knowledge detailed in this thesis is the development of a novel SAP compliant advanced dynamic calculation method (IDEAS) which guarantees that the SAP standard occupancy temperature profile is perfectly tracked and is also calibrated with SAP. The Inverse Dynamics based Energy Assessment and Simulation (IDEAS) method employs the perfect inverse control law RIDE to guarantee that the SAP standard occupancy temperature profile is met. IDEAS produces SAP compliant results and allows confident (i.e. calibrated in SAP) predictions to be made regarding the impact of novel heating and renewable energy systems. Researched in depth are the temperatures used in SAP, leading to analysis of the implications of tracking air temperature and various comfort temperatures. A focused evaluation of the treatment of renewables in SAP and DSMs is also presented, leading to suggestions which were implemented into the SAP framework. The role of real life monitoring in the energy assessment process is highlighted with monitored studies conducted. Also in this thesis case studies applying IDEAS to buildings with renewable heating systems are described. The IDEAS method employs SAP as an exemplar steady state calculation to highlight the successful use and calibration of a new advanced Inverse Dynamics based symbolic method. The philosophy, research and equations derived in IDEAS are presented in this thesis demonstrating their use in Microsoft Excel and Matlab / Simulink environments. The IDEAS methodology is transparent and portable. IDEAS can be applied to other methodologies, such as those employed by PHPP and SBEM (by carrying out a calibration process), and also to different simulation environments such as ESP-r and ESL (by adopting the IDEAS equations in those methods). The contribution to knowledge of IDEAS is demonstrated in this thesis by the development of the method and the use of SAP as a comparator. The IDEAS method has many uses outwith SAP which are highlighted in the cases studies and future work sections of this body of work

Adaptive load frequency control of electrical power systems

The thesis describes Load Frequency Control techniques which may be used for real-time on-line control of large electrical power systems. Traditionally the frequency control of power systems has been carried out using standard fixed parameter control schemes, which give control over the immediate steady- state error and the long term accumulated frequency error, but do not account for the fact that system conditions can alter due to the change in consumer load and generating patterns. The thesis presents a method of controlling the system frequency using adaptive control techniques, which ensure that optimal control action is calculated based on the present system conditions. It enables the system operating point to be monitored so that optimal control may continue to be calculated as the system operating point alters. The proposed method of frequency control can be extended to meet the problems of system interconnection and the control of inter-area power flows. The thesis describes the work carried out at Durham on a fixed parameter control scheme which led to the development of an adaptive control scheme. The controller was validated against a real-time power system simulator with full Energy Management software. Results are also presented from work carried out at the Central Electricity Research Laboratories under the C.A.S.E award scheme. This led to the development of a power system simulator, which along with the controller was validated on-line with the Dispatch Project used by the Central Electricity Generating Board

Model identification with application to building control and fault detection

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Architecture, 2004.Includes bibliographical references (p. 110-115).(cont.) may still be solved as an unconstrained linear least squares problem. To enforce the constraint on system eigenvalues, the problem is formulated as an unconstrained mixed (linear and non-linear) least-squares problem, which is easier to solve than the corresponding problem with linear objective function and non-linear constraints. The (usually unfounded) assumption on which the normal equations are based--that observations of the independent variables are error free--is relaxed at the cost of one more non-linear term. The resulting model coefficients are valid for predicting heat rate given zone temperature as well as for predicting zone temperature given heat rate. Control. Three important control applications involving transient zone thermal response are HVAC curtailment, optimal start, and night precooling. A general framework for model-based control of zone and whole-building operation is developed. Optimal precooling under time-of-use rates is formulated to solve the optimal fan operation sequence using a one-day control horizon with hourly time steps. Energy and demand cost savings are presented.Motivated by the high speed of real-time data acquisition, computational power, and low cost of generic PCs and embedded-PCs running Linux, this thesis addresses new methods and approaches to fault detection, model identification, and control. Fault detection: A series of faults was introduced into a 3-Ton roof-top air-conditioning unit (RTU). Supply and condenser fan imbalance were detected by changes in amplitude spectrum of real power resulting from the interaction of impeller rotation and the dominant chassis vibration mode. Ingestion of liquid refrigerant by the compressor was identified by detecting power and reactive power transients during compressor starts. An adaptive ARX(5) model was used to detect ingestion during steady compressor operation. Compressor valve or seal leakage were detected by a change in the leakage parameter of a simple evaporator-compressor-condenser model that explains the rise in compressor load from 0.25 to .5 seconds after compressor start, i.e. as shaft speed rises from about 50% to 90% of synchronous speed. Refrigerant undercharge was also detected by changes in start transient shape. Overcharge was detected by steady state compressor power and reduced evaporator and condenser air flow were detected by steady state power draw of the respective fan motors. Model Identification. On-line models are useful for control as well as fault detection. Model-based control of building loads requires a valid plant model and identification of such a model for a specific building or zone is a non-trivial inverse problem. The thesis develops three advances in the thermal diffusion inverse problem. Two involve thermodynamic constraints. The problem is first reformulated in such a way that the constraint on temperatureby Peter Ross Armstrong.Ph.D