Energy Performance Evaluation and Development of Control Strategies for the Air-conditioning System of a Building at Construction Stage

Energy consumption of HVAC systems in commercial buildings takes a great part of the total building energy consumption. Energy performance evaluation plays an important role in building energy efficiency improvement for existing buildings and new buildings. It is also the basis for the retrofitting measure evaluation for existing buildings and the control improvement evaluation of new buildings for building energy performance contracts. In this study, the energy performance evaluation of a super high-rising commercial office building in construction is presented. Alternative control strategies are proposed to improve the energy efficiency based on the current measurements of the original design as well as additional metering instruments as requested. These control strategies mainly involve optimal chiller sequencing control, cooling tower sequencing control, optimal water pressure differential set-point control, AHU supply air static pressure reset control and DCV-based fresh air control, etc. To assess the economic feasibility, the benchmark electricity consumption and the optimal electricity consumption using alternative controls strategies are estimated using dynamic simulations. The results show that the electricity savings using the alternative control strategies can cover the costs of an additional metering system and related software and hardware in about one year

Transmission Power Scheduling for Energy Harvesting Sensor in Remote State Estimation

We study remote estimation in a wireless sensor network. Instead of using a conventional battery-powered sensor, a sensor equipped with an energy harvester which can obtain energy from the external environment is utilized. We formulate this problem into an infinite time-horizon Markov decision process and provide the optimal sensor transmission power control strategy. In addition, a sub-optimal strategy which is easier to implement and requires less computation is presented. A numerical example is provided to illustrate the implementation of the sub-optimal policy and evaluation of its estimation performance.Comment: Extended version of article to be published in the Proceedings of the 19th IFAC World Congress, 201

A 2d-Numerical Study on Slot Jet Applied to a Wind Turbine as a Circulation Control Technique

The file attached to this record is the author's final peer reviewed version.A study on the feasibility of the Circulation Control (CC) technique for wind turbines is proposed. The CC was born in aeronautic field to improve the lift force on the wings, allowing the short take-off and landing of aircraft. It consists in blowing air at a relatively high speed over a rounded trailing edge. The thin jet of air remains attached to the convex curved surface, imposing a certain curvature to the outer streamlines, and, hence, increasing the lift force of the airfoil. Aim of this study is to numerically investigate the advantages on a wind turbine, based on the S809 airfoil, taking into account the energy related considerations, as the cost of the jet production. The paper, after a thorough evaluation of the increase of the generated power, finds that this technique could be promising in the energy harvesting aim

Comparison of CSMA based MAC protocols of wireless sensor networks

Energy conservation has been an important area of interest in Wireless Sensor networks (WSNs). Medium Access Control (MAC) protocols play an important role in energy conservation. In this paper, we describe CSMA based MAC protocols for WSN and analyze the simulation results of these protocols. We implemented S-MAC, T-MAC, B-MAC, B-MAC+, X-MAC, DMAC and Wise-MAC in TOSSIM, a simulator which unlike other simulators simulates the same code running on real hardware. Previous surveys mainly focused on the classification of MAC protocols according to the techniques being used or problem dealt with and presented a theoretical evaluation of protocols. This paper presents the comparative study of CSMA based protocols for WSNs, showing which MAC protocol is suitable in a particular environment and supports the arguments with the simulation results. The comparative study can be used to find the best suited MAC protocol for wireless sensor networks in different environments.Comment: International Journal of AdHoc Network Systems, Volume 2, Number 2, April 201

Evaluation of the energy impact of PCM tiles in an Airport Terminal Departure hall

Copyright @ 2013 CIBSEIn most past studies, passive PCM (phase change materials) systems have been tested for relatively small office spaces where the airflow is of minimal consequence in the overall energy consumption of the space. This paper on the other hand, reports on the application of PCM tiles on the floor of an Airport terminal space, similar to London Heathrow Terminal 5 departure hall, where in such large open spaces, the influence of airflow is crucial for the evaluation of the energy performance of AC units. In this paper, the evaluation of the energy performance of PCM tiles is obtained through a coupled simulation of TRNSYS and CFD. TRNSYS simulates the AC unit and PID control systems, while CFD is used to simulate the airflow and radiation inside the terminal space. The phase change process is simulated in CFD using an in-house developed model which considers hysteresis effects and the non-linear enthalpy-temperature relationship of PCMs. Although, a displacement ventilation (DV) system is actually employed at Heathrow Terminal 5, this study also compares the performance of the PCM tiles for a mixed ventilation (MV) system. Due to large computing times associated with CFD, discrete time-dependent scenarios under different UK weather conditions are used. The yearly energy demand is then determined through the heating/cooling degree day concept using base temperatures of 18 and 23 °C for HDD and CDD, respectively, similar to the comfort temperature range in the Terminal. The results show that the use of PCM tiles on the floor of the Terminal departure hall can lead to annual energy savings of around 3% for the DV system and 6% for the MV system, corresponding to 174 MWh/year and 379 MWh/year for the Terminal building.This work was funded by the UK Engineering and Physical Sciences Research Council (EPSRC), Grant No: EP/H004181/1

The environmental effect of car-free housing: A case in Vienna

A case-control study of the car-free model housing project in Vienna was conducted to evaluate whether people living in this settlement have more [`]sustainable lifestyles' than people living in comparable buildings in Vienna. Another aim was to identify the lifestyle characteristics and household activities which significantly influence the environmental impact of the residents of the car-free housing project and a control group. The control group, referred to as the reference settlement, was chosen from a nearby building complex, with similar characteristics, but without the car-free feature. Household consumption patterns were estimated based on interviews in combination with data from the Austrian consumer expenditure survey and the national accounts. The evaluation of household environmental impacts uses emissions estimates from the Austrian national accounting matrices including environmental accounts and data from life-cycle assessments. Households from the car-free settlement have substantially lower environmental impacts in the categories of ground transportation and energy use; their CO2 emissions of these two categories are less than 50% of those living in the reference settlement. The households in the car-free settlement have somewhat higher emissions in the categories air transport, nutrition, and [`]other' consumption, reflecting the higher income per-capita. As a result, the CO2 emissions are only slightly lower than in the reference settlement, but the emissions intensity is 20% lower. Both household groups have significantly lower environmental impacts than the Austrian average reflecting less car use and cleaner heating energy in Vienna