Information Technology for Energy and Maintenance Management

We describe the design of a tenant interface for energy and maintenance systems (TIEMS) in commercial buildings. TIEMS is designed for use by occupants (tenants) of commercial buildings. Our hypothesis is that by allowing tenants access to information from the energy and maintenance systems and by giving them some control over these systems, energy and maintenance performance can be improved. We used interviews with potential users and existing energy and maintenance databases to guide the design. Results of a field trial demonstrate the utility of TIEMS. We also describe the design of a maintenance and operations recommender (MORE). MORE uses information from computerized maintenance management systems (CMMS) and energy management and control systems (EMCS) to recommend what maintenance personnel should do in response to a maintenance service request. MORE integrates text descriptions of problems with sensor information related to the problem. After work orders are closed, MORE uses the information about what was actually done to solve the problem to learn how to improve its recommendations

A Thermal Sensation Index for Real-Time Tuning and Energy-Optimal Control of HVAC Systems

In this paper we discuss and develop a thermal comfort index that addresses the limitations of applying thermal comfort indices to control applications. The derivation closely follows the derivation of PMV, but certain changes and simplifications make the index an explicit, linearly parameterized function of environmental variables. We show that the differences between the derivation of this index and the derivation of PMV do not reduce the accuracy of the index in comparison to PMV. Since this index is linearly parameterized, the parameters can be quickly and efficiently tuned in real time to reflect the thermal sensation of the specific occupant. Parameter tuning makes it possible to accurately predict the thermal sensation of the occupant without exact knowledge of the activity level or clothing insulation of the occupant when these two quantities are known to be constant. Additionally, the tuning process makes the thermal sensation prediction relatively insensitive to sensor location because biases and scaling errors are absorbed by the estimated parameters. Real-time parameter tuning is demonstrated experimentally for a seated, stationary occupant. The feasibility of using variable air flow and variable heat flow to regulate the thermal sensation index in a way that minimizes power consumption is investigated. The simplified index provides a quantitative means for determining the most energy efficient comfortable conditions. The analysis demonstrates that for low to moderate outdoor relative humidity there is an energy optimal combination of air flow and heat flow

Multi-Sensor Single-Actuator Control of HVAC Systems

It is common to control several rooms in a building with a single sensor in one of the rooms and a single actuator driving just one control element such as an air damper. New, low-cost, wireless sensor technology now offers the opportunity to replace the single sensor in one room with a network of sensors having at least one sensor per room. This paper addresses this multi-sensor, single-actuator control problem. We used computer simulations and optimization to study the problem. We designed a computer simulation of the heat transfer behavior of a section of a building that accounted for the effects of weather, building materials, ventilation, and loads from occupants and equipment. We considered ad hoc methods (such as averaging) of using information from multiple sensors. We also developed a new, model-free method of using information from multiple sensors that is based on a simple optimization procedure. The optimization procedure can be configured to optimize comfort or to optimize energy under comfort constraints. We compared the performance of the single-sensor strategy with the ad hoc strategies and optimized strategies using annual simulations of a four-room, perimeter section of a building and weather data from Sacramento, California. We report heating and cooling energy performance along with two comfort metrics, the average number of rooms within the ASHRAE comfort zone and the Predicted Percentage Dissatisfied (PDD). The results show that most of the multi-sensor control strategies do better than the single-sensor strategy on the basis of both energy performance and comfort. The energy-optimal strategy reduces energy consumption by 17% while reducing PDD from 30% to 24%. The comfort-optimal strategy reduces energy consumption by 4% while reducing PPD from 30% to 20%. The performance improvements occur primarily when the average load among all rooms is nearly zero, with some rooms requiring heating while others require cooling. Under these conditions, the single-sensor strategy either overcools or overheats, whereas the multi-sensor strategies use almost no energy

Opportunities to Save Energy and Improve Comfort by Using Wireless Sensor Networks in Buildings

This paper discusses how intensive information technology can affect future building operation. Recent breakthroughs in wireless sensor network technology will permit 1) highly flexible location of sensors, 2) increased sensing density and variety of sensor types informing more comprehensive control systems, 3) occupants' involvement in control loops, 4) demand responsive electricity management, 5) integration among now-separate building systems, and 6) the adoption of mixed-mode and other new types of air conditioning systems. The paper describes the capabilities of the new sensor networks, assesses how some applications can increase the quality of control and improve energy efficiency, and suggests opportunities for future development

Coordinated Control of HVAC Systems

This paper describes the development of new control logic for starting and stopping energy-intensive equipment in buildings such as staged air-conditioning units. The concept is to use pulse-width modulation (PWM) instead of level-crossing logic. A finite state machine is used to handle the case where a single unit has multiple stages of operation. An optimized coordinator determines the phase of the PWM signals of each unit so that peak demand for power is minimized over each PWM period. Control logic for the PWM function was developed so that the phase could be manipulated by the coordinator. Computer simulations were used to assess the performance of the new strategy and to compare it to levelcrossing logic. The following five metrics were used to assess the performance: 1) magnitude of the control error, 2) start/stop frequency, 3) average power consumption, 4) standard deviation of the power consumption, 5) peak power consumption. The computer simulations showed that the new strategy could reduce peak power consumption by 20% relative to level-crossing logic. The computer simulations also showed that the new strategy increased the magnitude of the space temperature control error by 11% and increased the number of start/stop operations by 27% relative to level-crossing logic

Cepheid Calibration of the Peak Brightness of SNe Ia -- IX. SN 1989B in NGC 3627

(Abridged) Repeated imaging observations have been made of NGC 3627 with the HST in 1997/98, over an interval of 58 days. Images were obtained on 12 epochs in the F555W band and on five epochs in the F814W band. The galaxy hosted the prototypical, `Branch normal', type Ia supernova SN 1989B. A total of 83 variables have been found, of which 68 are definite Cepheid variables with periods ranging from 75 days to 3.85 days. The de-reddened distance modulus is determined to be (m-M)_0= 30.22+/-0.12 (internal uncertainty) using a subset of the Cepheid data whose reddening and error parameters are secure. The photometric data of Wells et al. (1994), combined with the Cepheid data for NGC 3627 give M_B(max)= -19.36+/-0.18 and M_V(max)= -19.34+/-0.16 for SN 1989B. Combined with the previous six calibrations in this program, plus two additional calibrations determined by others gives the mean absolute magnitudes at maximum of = -19.48+/-0.07 and = -19.48 +/-0.07 for `Branch normal' SNe Ia at this interim stage in the calibration program. The second parameter correlations of M(max) of blue SNe Ia with decay rate, color at maximum, and Hubble type are re-investigated. The dependence of on decay rate is non-linear, showing a minimum for decay rates between 1.0< Delta m_15 <1.6. Magnitudes corrected for decay rate show no dependence on Hubble type, but a dependence on color remains. Correcting both the fiducial sample of 34 SNe Ia with decay-rate data and the current 8 calibrating SNe Ia for the correlation with decay rate as well as color gives H_0= 60+/-2 (internal) km/s/Mpc, in both B and V. The same value to within 4% is obtained if only the SNe Ia in spirals (without second parameter corrections) are considered.Comment: 32 pages (with 7 tables and 14 figures) LaTeX, uses emulateapj.sty; a full-resolution version with complete figs. 4 and 5 is available at http://www.astro.unibas.ch/cosmology/papers.html ; accepted for publication in Ap

Striatal responsiveness to reward under threat-of-shock and working memory load: A preliminary study.

Reward and stress are important determinants of motivated behaviors. Striatal regions play a crucial role in both motivation and hedonic processes. So far, little is known on how cognitive effort interacts with stress to modulate reward processes. This study examines how cognitive effort (load) interacts with an unpredictable acute stressor (threat-of-shock) to modulate motivational and hedonic processes in healthy adults. A reward task, involving stress with unpredictable mild electric shocks, was conducted in 23 healthy adults aged 20-37 (mean age: 24.7 ± 0.9; 14 females) during functional magnetic resonance imaging (fMRI). Manipulation included the use of (a) monetary reward for reinforcement, (b) threat-of-shock as the stressor, and (c) a spatial working memory task with two levels of difficulty (low and high load) for cognitive load. Reward-related activation was investigated in a priori three regions of interest, the nucleus accumbens (NAcc), caudate nucleus, and putamen. During anticipation, threat-of-shock or cognitive load did not affect striatal responsiveness to reward. Anticipated reward increased activation in the ventral and dorsal striatum. During feedback delivery, both threat-of-shock and cognitive effort modulated striatal activation. Higher working memory load blunted NAcc responsiveness to reward delivery, while stress strengthened caudate nucleus reactivity regardless reinforcement or load. These findings provide initial evidence that both stress and cognitive load modulate striatal responsiveness during feedback delivery but not during anticipation in healthy adults. Of clinical importance, sustained stress exposure might go along with dysregulated arousal, increasing therefore the risk for the development of maladaptive incentive-triggered motivation. This study brings new insight that might help to build a framework to understand common stress-related disorders, given that these psychiatric disorders involve disturbances of the reward system, cognitive deficits, and abnormal stress reactivity

Observation of a critical pressure gradient for the stabilization of interchange modes in simple magnetized toroidal plasmas

The existence of a critical pressure gradient needed to drive the interchange instability is experimentally demonstrated in the simple magnetized torus TORoidal Plasma EXperiment [A. Fasoli et al., Phys. Plasmas 13, 055902 (2006)]. This gradient is reached during a scan in the neutral gas pressure pn. Around a critical value for pn, depending on the magnetic configuration and on the injected rf power, a small increase in the neutral gas pressure triggers a transition in the plasma behavior. The pressure profile is locally flattened, stabilizing the interchange mode observed at lower neutral gas densities. The measured value for the critical gradient is close to the linear theory estimate

Addressing Grand Challenges in Earth Observation Science: The Earth Observation Data Centre for Water Resources Monitoring

Earth observation is entering a new era where the increasing availability of free and open global satellite data sets combined with the computing power offered by modern information technologies opens up the possibility to process high-resolution data sets at global scale and short repeat intervals in a fully automatic fashion. This will not only boost the availability of higher level earth observation data in purely quantitative terms, but can also be expected to trigger a step change in the quality and usability of earth observation data. However, the technical, scientific, and organisational challenges that need to be overcome to arrive at this point are significant. First of all, Petabyte-scale data centres are needed for storing and processing complete satellite data records. Second, innovative processing chains that allow fully automatic processing of the satellite data from the raw sensor records to higher-level geophysical products need to be developed. Last but not least, new models of cooperation between public and private actors need to be found in order to live up to the first two challenges. This paper offers a discussion of how the Earth Observation Data Centre for Water Resources Monitoring (EODC) – a catalyser for an open and international cooperation of public and private organisations – will address these three grand challenges with the aim to foster the use of earth observation for monitoring of global water resources