Annual Electricity Savings Research Articles

Framework for Energy Efficiency White Certificates in the Emirate of Abu Dhabi

Abstract Energy efficiency in the demand side is considered one of the cheapest ways to achieve reductions in Green House Gases emission, as well as to avoid heavy investments in production, transmission and distribution of electricity. In the context of the Emirate of Abu Dhabi, UAE, where buildings (residential, office, retail and villas) consume about 87% of the electricity, most of which is devoted to indoor air-conditioning, energy efficiency has a huge potential for development. Under the current political/economical scenario, a series of measures to diversify the economy and attract expatriates are in place. These include heavy subsidies on retail electricity prices—which has the side-effect of limiting the economic feasibility of investments in energy efficiency. In this study, a series of building retrofits were tested on a model of the average office building in the Emirate. The best performing retrofit was identified to be the chiller's Coefficient of Performance (COP) improvements, having the lowest cost/benefit ratio and resulting in an overall annual electricity savings of around 12%. Under the current subsidized electricity price, investments in energy efficiency of existing buildings are not attractive for the owner-consumer, as over the lifecycle of the measure, the return on investment is low or negative. In this paper we attempt to assess the applicability, in the Emirate of Abu Dhabi, of energy saving obligations and tradable white certificates as a mechanism to enable investment in demand-side energy efficiency and achieving average investment returns of 7% over a 25 years horizon. The application of white certificates can enable the market of energy efficiency to develop in the Emirate. The economic return of applying a chiller retrofit under the studied white certificate scenario avoids the increase of 17% of current electricity prices.

Field evaluation of advanced controls for the retrofit of packaged air conditioners and heat pumps

Abstract This paper documents the magnitude of energy savings achievable in the field by retrofitting existing packaged rooftop air conditioner and heat pump units (RTUs) with advanced control strategies not ordinarily used for RTUs. A total of 66 RTUs on 8 different buildings were retrofitted with a commercially available advanced controller for improving operational efficiency. The controller features enhanced air-side economizer control, multi-speed fan control, and demand-controlled ventilation. Of the 66 RTUs, 18 are packaged heat pumps and the rest are packaged air conditioners with gas heat. The eight buildings cover four building types and four climate conditions. Based on the performance data collected for approximately 1 year, the normalized annual energy consumption savings ranged between 22% and 90%, with an average of 57% for all RTUs. The average fractional savings uncertainty was 12% at 95% confidence level. Normalized annual electricity savings were in the range between 0.47 kW h/h (kW h per hour of RTU operation) and 7.21 kW h/h, with an average of 2.39 kW h/h. RTUs greater than 53 kW and runtime greater than 14 h per day had payback periods less than 3 years even at electricity price of $0.05/kW h.

Central Plant Control Optimization with a Thermal Chilled Water Energy Storage System: A Case Study in a High-Tech Building

The paper presents the study on the control optimization of the central cooling plant system including thermal chilled water energy storage (TES) tank in a high-tech building consists of office area, clean room and lab space. The optimized control sequences were implemented on the cooling tower staging, cooling tower fan/condenser water pump/primary chilled water pump staging and speed control, chiller staging, TES pump speed and TES modulation valves control, and secondary chilled water loop differential pressure control. The proposed control effectively resolved the problem of fluctuation in the secondary chilled water supply temperature during charging cycle and temperature increase during the discharging cycle. The number of primary chilled water pumps, condenser water pumps and cooling tower fans were also reduced to minimum after the optimization. Implementation of optimized control sequences is predicted to have an annual electricity savings of 856,125 kWh, which is about 20% of the total central plant energy consumption.

Engineering design and assessment of a demand-sensitive LED streetlighting system

A solid-state lighting technology was demonstrated at a US Navy Research Center in Maryland – where light-emitting diode (LED) luminaires were substituted for existing high pressure sodium (HPS) streetlighting units, and an intelligent lighting control system was deployed. This paper summarizes the prudent engineering design and implementation of the demand-sensitive feature of the LED streetlighting system at Naval Surface Warfare Center (NSWC) Carderock Division that provides an annual average electricity and CO2 savings of 74%. In addition, technical system performance and life-cycle assessment of the HPS and the new LED systems are discussed. Best practices and field experience that can help with other similar smart lighting implementation elsewhere are also summarized.

An investigation of coupling evaporative cooling and decentralized graywater treatment in the residential sector

Total electricity and water burdens, including both direct and indirect uses, were modeled for newly constructed and 15-year-old homes in six California climate zones for three air conditioning systems: standard air-cooled condensing unit, evaporatively pre-cooled condensing unit, and an evaporative condensing unit. Compared to the air-cooled condensing unit, average annual direct electricity savings were 17.7% and 11.3% for an evaporatively pre-cooled condensing unit and an evaporative condensing unit, respectively. The evaporative condensing unit provided greater savings at peak load than the evaporatively pre-cooled condensing units (peak power savings were 30.9% and 23.8%, respectively), which is promising for hot arid climates. Total water burden reflected direct (e.g., evaporation) and indirect (i.e., electricity generation) water use. The standard air-cooled condensing unit, which had only an indirect water burden, exhibited the lowest total water burden; the evaporatively pre-cooled condensing unit and evaporative condensing unit had similar total water burdens, which were approximately double the air-cooled condensing unit's total water burden. This is because the evaporatively pre-cooled condensing unit and evaporative condensing unit both required a substantial volume of water (average 30.8 and 28.1 L/h, respectively; up to 8.5% increased water consumption for a typical household) to achieve their electricity-saving and peak power reduction benefits. This additional water burden can be offset by implementing an in-home decentralized graywater treatment and reuse plan, where shower and clothes-wash water is treated and recycled in-home for evaporative cooling as well as irrigation and toilet flushing.

Energy-saving analysis of telecommunication base station with thermosyphon heat exchanger

In Chinese telecommunication base stations, the air conditioning energy consumption is almost 47% of the total energy consumption. However, air-to-air thermosyphon heat exchangers can be used in winter, early spring and late autumn to cool the buildings using the outdoor ambient air to significantly decrease the power consumption. An energy consumption model was built based on the indoor environmental building requirements and a combined air conditioner and thermosyphon heat exchanger system. The building heat load and energy consumption were calculated for typical cities in China assuming 50mm thick sandwich panels as the envelope material. The cooling/heating load, annual electricity savings, annual energy savings and static payback periods for combined system were compared with those for just an air conditioner. A national distribution map was then developed to show the annual energy savings in China for different climate zones. The thermosyphon heat exchanger provides remarkable energy savings. About 87% of all cities in China lie in cold and moderate zones suitable for applications. The annual energy savings is over 30%. The static payback period decreases with increasing annual energy savings with average static payback periods for most cities in China of about 4.3years.

Assessing the technical and economic viability of low-cost domestic solar hot water systems (DSHWS) in low-income residential dwellings in Brazil

Abstract Domestic solar hot water systems (DSHWS) have been used worldwide for many decades. Activities in this area are usually targeting middle- or upper-class residential dwellings, and solar collector design and sizing is carried out aiming at this market. In developing countries of the sunbelt, however, there is a huge potential for low-cost DSHWS in low-income residential dwellings. We have assessed the technical and economic viability of this technology, both from the electric utility's perspective, and from the standpoint of low-income residential consumers. We have analysed data of 12 months of continuous monitoring of a statistically representative sample of consumers at a low-income residential building in Florianopolis – Brazil (27°S, 1550 kWh/m 2 /year solar irradiation average). We have studied the power consumption of 60 residential units equipped with a commercially available, low-cost DSHWS, and a 30 units control group, where hot water was supplied with the electronic showerhead typical of Brazilian dwellings. Annual electricity savings averaged 38%, and peak-time electricity demand was reduced by 42%. For discount rates of up to 9.5%, this technology is attractive from a utility's perspective for large-scale deployment. The financial benefit from avoided CO 2 emissions has limited economic attractiveness, and can only be justified under a large-scale deployment program.

Novel instrumentation for monitoring after-hours electricity consumption of electrical equipment, and some potential savings from a switch-off campaign

An increasing cause of electricity use and greenhouse gas emissions is from IT equipment such as computers, printers, and servers, with worldwide computer use increasing from 1000 million PCs in 2006, to 1400 million in 2010, and estimated to cause 3% of global electricity demand. Significant energy may be saved if un-used devices are switched off. It was noted that the switch-off rates in the USA for desktop computers in 2006, could be as low as 30%, and there clearly is a need for up-to-date information. It has been difficult to provide accurate figures for switch-off rates, since previous monitoring of IT use has been expensive, requiring specialised equipment and electrical work, labour intensive (using walk-through surveys), or both. This paper demonstrates two low-cost techniques for estimation of unoccupied PC use. Precision and tracking for both were compared with actual power consumption, and subcircuit switch-off rates appeared to be under 76%. Whole building IT related use (including servers) was around 40% of electrical baseload. A desktop switch-off campaign was instigated for accessible equipment, resulting in a 20% reduction in electrical baseload. Extrapolation to a weeknight campaign suggests annual electricity savings of around 12%.

Energy efficiency in energy-intensive industries—an evaluation of the Swedish voluntary agreement PFE

In this paper, we evaluate the Swedish Programme for improving energy efficiency in energy-intensive industries (PFE). Since 2005, some 100 energy-intensive companies have entered this 5-year voluntary agreement (VA) and been exempted from the EU minimum tax on electricity. In return, each company is required to: conduct an energy audit and analysis; identify and invest in profitable electricity saving measures; implement and certify an energy management system; introduce routines for energy efficient procurement and project planning. For most participants the first programme period was completed in 2009 and available data enables this PFE ex-post evaluation. An impact evaluation compiles and analyse data that the companies have reported to the administrating agency, the Swedish Energy Agency (SEA). This assessment of quantifiable results is complemented by a process-oriented approach that combines studies of policy documents, previous evaluations and personal communication with administrators as well as companies. The bottom-up calculation method distinguishes between gross and net impact. While the SEA estimates a gross impact of 1,450 GW h/year, the net impact consists of an interval between 689 and 1,015 GW h of net annual electricity savings. PFE has effectively and, to a low cost, exceeded the estimated impact of a minimum tax and can thus be judged as successful. A comprehensive evaluation plan could facilitate relevant data gathering in PFE and similar VAs and could, in doing so, improve accuracy and possibly reduce evaluation cost. Such a plan should give weight also to the organisational changes, with potential long-lasting effects, that these programmes are capable of promoting.

Effect of External Wall Insulation on Building Energy Consumption

The building energy consumption associated with the external wall insulation for different orientations and different exterior finishes has been evaluated using the simulation software EnergyPlus. The results suggest that in certain condition the thermal resistance of the external wall and the absorptance of the exterior finish should be high for heating dominated climate or room, while both of them should be low for cooling dominated climate or room for saving energy. Besides, it has different annual electricity savings for different external wall orientations at the same thickness of thermal insulation, so the insulation should be priority used for the external wall which has the largest saving potential.

Calculating energy-saving potentials of heat-island reduction strategies

We have developed summary tables (sorted by heating- and cooling-degree-days) to estimate the potential of heat-island reduction (HIR) strategies (i.e., solar-reflective roofs, shade trees, reflective pavements, and urban vegetation) to reduce cooling-energy use in buildings. The tables provide estimates of savings for both direct effect (reducing heat gain through the building shell) and indirect effect (reducing the ambient air temperature). In this analysis, we considered three building types that offer the most savings potential: residences, offices, and retail stores. Each building type was characterized in detail by Pre-1980 (old) or 1980 + (new) construction vintage and with natural gas or electricity as heating fuel. We defined prototypical-building characteristics for each building type and simulated the effects of HIR strategies on building cooling- and heating-energy use and peak power demand using the DOE-2.1E model and weather data for about 240 locations in the US. A statistical analysis of previously completed simulations for five cities was used to estimate the indirect savings. Our simulations included the effect of (1) solar-reflective roofing material on building ( direct effect), (2) placement of deciduous shade trees near south and west walls of building ( direct effect), and (3) ambient cooling achieved by urban reforestation and reflective building surfaces and pavements ( indirect effect). Upon completion of estimating the direct and indirect energy savings for all the locations, we integrated the results in tables arranged by heating- and cooling-degree-days. We considered 15 bins for heating-degree-days, and 12 bins for cooling-degree-days. Energy use and savings are presented per 1000 ft 2 of roof area. In residences heated with gas and in climates with greater than 1000 cooling-degree-days, the annual electricity savings in Pre-1980 stock ranged from 650 to 1300 kWh/1000 ft 2; for 1980 + stock savings ranged 300–600 kWh/1000 ft 2. For residences heated with electricity, the savings ranged from 350 to 1300 kWh/1000 ft 2 for Pre-1980 stock and 190–600 kWh/1000 ft 2 for 1980 + stocks. In climates with less than 1000 cooling-degree-days, the electricity savings were not significantly higher than winter heating penalties. For gas-heated office buildings, simulations indicated electricity savings in the range of 1100–1500 kWh/1000 ft 2 and 360–700 kWh/1000 ft 2, for Pre-1980 and 1980 + stocks, respectively. For electrically heated office buildings, simulations indicated electricity savings in the range of 700–1400 kWh/1000ft 2 and 100–700 kWh/1000 ft 2, for Pre-1980 and 1980 + stocks, respectively. Similarly, for gas-heated retail store buildings, simulations indicated electricity savings in the range of 1300–1700 kWh/1000 ft 2 and 370–750 kWh/1000 ft 2, for Pre-1980 and 1980 + stocks, respectively. For electrically heated retail store buildings, simulations indicated electricity savings in the range of 1200–1700 kWh/1000 ft 2 and 250–750 kWh/1000 ft 2, for Pre-1980 and 1980 + stocks, respectively.

Cooling energy savings potential of reflective roofs for residential and commercial buildings in the United States

We make quantitative estimates of the impact of roof reflectivity on cooling and heating energy use for buildings in the US. Prototypical buildings are simulated with reflective (light in color) and absorptive (dark in color) roofs. Differences of annual cooling and heating energy use and peak electricity demand between dark and light roofs yield the savings. The DOE-2 building energy simulation program is used for these calculations. Monetary savings are calculated using local utility rates. Savings are estimated for 11 US metropolitan statistical areas (MSAs) in a variety of climates. The total savings for all 11 MSAs are: annual electricity savings, 2.6 terawatt hours (TWh); net annual savings, $194 M; and peak electricity demand savings, 1.7 gigawatt (GW). Extrapolating the savings from the 11 MSAs to the entire United States, we estimate annual electricity savings of about 10 TWh and a net savings of about $750 M in annual energy payments. Peak electricity power reduction is estimated to be about 7 GW.

Impacts of Large-Scale Surface Modifications on Meteorological Conditions and Energy Use: A 10-Region Modeling Study

This paper summarizes results from a mesoscale modeling study to quantify the possible meteorological and energy-use impacts of large-scale increases in surface albedo and vegetative fraction. Ten regions in the U.S. were characterized and simulated in base- and modified-surface conditions. Time- and space-dependent meteorological variables were simulated for each region in four 3-day episodes to represent a range of seasonal variations. Using a simple interpolative procedure, a complete year of hourly weather data was created for each region (based on episodic meteorological simulation results) and input into energy-use models. The modified weather input was used to assess the effects of large-scale albedo and vegetative fraction changes on annual energy consumption in each of the ten areas targeted in this study. The simulations suggest annual electricity savings of between 1and 6.7 kWh m−2 (of roof area) in residential neighborhoods and between 2 and 6.1 kWh m−2 in office areas, depending on region. Annual gas penalties amount to up to 34.8 MJ m−2 (of roof area) in residential neighborhoods and up to 21.1 MJ m−2 in office areas.

97/02896 Electrical energy and cost savings potential at DOD facilities

The US Department of Defense (DOD) has been mandated to reduce energy consumption and costs by 20% from 1985 to 2000 and by 30% from 1985 to 2005. Reduction of electrical energy consumption at DOD facilities requires a better understanding of energy consumption patterns and energy and financial savings potential. This paper utilizes two independent studies--EDA (End-Use Disaggregation Algorithm) and MEIP (Model Energy Installation Program)--and whole-installation electricity use data obtained from a state utility to estimate electrical energy conservation potential (ECP) and cost savings potential (CSP) at the Fort Hood, Texas, military installation and at DOD nationwide. At Fort Hood, the authors estimated an annual electricity savings of 62.2 GWh/yr (18%), a peak demand savings of 10.1 MW (14%), and an annual energy cost savings of $6.5 million per year. These savings could be attained with an initial investment of $41.1 million, resulting in a simple payback of 6.3 years. Across the DOD, they estimated an annual electricity savings of 4,900 GWh/yr, a peak demand savings of 694 MW, and an annual energy cost savings of $316 million per year. The estimated cost savings is 16% of the total nationwide DOD 1993 annual energy costs. These savings could be attainedmore » with an initial investment of $1.23 billion, resulting in a simple payback of 3.9 years.« less

A pump economizer for evaporative coolers

The water flow rate in the existing evaporative coolers used in India for domestic cooling (called “desert coolers” in the local markets) is much higher than what is required to keep the fibre pads wet. Therefore, a retrofit has been designed to lower the electrical energy consumption of the coolers. We report here on the design, performnace and economics of the proposed retrofit which can be very easily fitted to existing coolers. The cost of the retrofit, including installation charges, is about Rs. 95 (1988 rupees) or about US$ 6 (US$ 1 = Rs. 15.60), and the resulting annual electricity savings are about 25 kWh. Since space cooling contributes to the summertime peak electricity demand in large North Indian urban centres such as Delhi, the device appears very attractive for conserving electrical energy and peak urban electricity demand in summertime.

Electricity savings one, two, and three years after participation in the BPA Residential Weatherization Pilot Program

The Bonneville Power Administration (BPA) operated a Residential Weatherization Pilot Program from 1980 through 1982. The program provided free home energy audits to 7200 electrically heated homes in the Pacific Northwest and gave zero-interest loans to weatherize 4100 of these homes. The total cost of the program was almost $11 million. This paper estimates the energy-saving effects of the BPA program. The data used include one year of preprogram and three years of postprogram electricity consumption records. The first stage of our method involves estimation of weather-adjusted annual electricity consumption for each household. The second stage uses this weather-adjusted consumption as the dependent variable in a pooled time-series/cross-section regression model of electricity use. The total annual electricity savings experienced by the households that received both an energy audit and a weatherization loan averaged 19 GJ elec/year one year after participation, increasing to 22 GJ elec and 23 GJ elec two and three years after participation. The net annual electricity savings that can be directly attributed to the BPA pilot program for these households averaged 16 GJ elec (15% of preprogram use) one year after participation and declined to 15 GJ elec two years and three years after participation. Program-related savings decrease over time, presumably because participants would have been stimulated by other factors (especially rapidly rising electricity price) to adopt conservation actions.