Carbon Free Boston: Energy Technical Report

Part of a series of reports that includes: Carbon Free Boston: Summary Report; Carbon Free Boston: Social Equity Report; Carbon Free Boston: Technical Summary; Carbon Free Boston: Buildings Technical Report; Carbon Free Boston: Transportation Technical Report; Carbon Free Boston: Waste Technical Report; Carbon Free Boston: Offsets Technical Report; Available at http://sites.bu.edu/cfb/INTRODUCTION: The adoption of clean energy in Boston’s buildings and transportation systems will produce sweeping changes in the quantity and composition of the city’s demand for fuel and electricity. The demand for electricity is expected to increase by 2050, while the demand for petroleum-based liquid fuels and natural gas within the city is projected to decline significantly. The city must meet future energy demand with clean energy sources in order to meet its carbon mitigation targets. That clean energy must be procured in a way that supports the City’s goals for economic development, social equity, environmental sustainability, and overall quality of life. This chapter examines the strategies to accomplish these goals. Improved energy efficiency, district energy, and in-boundary generation of clean energy (rooftop PV) will reduce net electric power and natural gas demand substantially, but these measures will not eliminate the need for electricity and gas (or its replacement fuel) delivered into Boston. Broadly speaking, to achieve carbon neutrality by 2050, the city must therefore (1) reduce its use of fossil fuels to heat and cool buildings through cost-effective energy efficiency measures and electrification of building thermal services where feasible; and (2) over time, increase the amount of carbon-free electricity delivered to the city. Reducing energy demand though cost effective energy conservation measures will be necessary to reduce the challenges associated with expanding the electricity delivery system and sustainably sourcing renewable fuels.Published versio

Application of passive solar design strategies for residential houses with different construction systems in NSW, Australia

Energy consumed in active heating, ventilation and cooling accounts for about 40 per cent of the total energy used in a typical Australian house. Passive solar design, by which one can take advantage of the natural climate, is found to be one of the key methods to minimise or even sometimes eliminate the need for active heating and cooling energy. The passive solar design includes consideration of the building orientation and careful design of the building envelope, such as roof, walls, windows, floor systems and thermal mass; with an overall aim of controlling the heat flow in or out of the building. The main aim of this study is to demonstrate the opportunity of energy conservation between houses with different construction systems that varies in thermal mass. A number of test houses, detached dwellings on a typical land area of 400 m2, were used to achieve the objective via parametric simulation of a series of scenarios. The simulation scenarios were based on different sub-flooring construction systems and walls. Integrated shading devices, thermal mass, orientation, and glazing, along with ventilation and infiltration rates, were considered in each scenario with different compositions. Internal air movement between the two floors of a two-storey house was simulated in each of the scenarios by calculating the air movement through the staircase. These analyses were carried out using commercially available off-the-shelf Building Energy simulation software called IDA Indoor Climate and Energy (IDA ICE). The energy saving values over the life span of the building were computed and compared between the standard houses which do not have passive solar design strategies and improved houses, which incorporate passive solar design strategies. The results show that the, improved houses are more energy efficient and cost-effective than standard houses over the considered life span of 50 years. Applying Passive solar and Energy Efficiency Design Strategies (PSEEDS) to old fibro and modern brick houses effectively reduced the total energy required for cooling and heating by 43% and 46%, respectively. Increasing the thermal mass of a house using, for example, a concrete slab for flooring and brick veneer walls, can significantly reduce the annual energy requirements of both standard and improved houses by 35% and 39%, respectively. Hence, a typical brick veneer house is more energy efficient than a typical fibro house. In addition, when a brick veneer house (which is a most common modern construction in Australia), is incorporated with PSEEDS, it is possible to reduce energy consumption by as much as 65% compared to a standard fibro house. In addition, the improved reverse brick veneer house performed better than the improved brick veneer system by 24%. The results obtained in this study indicate that the reverse brick veneer houses are more energy efficient than alternative construction systems over their lifetime

DTT - Divertor Tokamak Test facility - Interim Design Report

The “Divertor Tokamak Test facility, DTT” is a milestone along the international program aimed at demonstrating – in the second half of this century – the feasibility of obtaining to commercial electricity from controlled thermonuclear fusion. DTT is a Tokamak conceived and designed in Italy with a broad international vision. The construction will be carried out in the ENEA Frascati site, mainly supported by national funds, complemented by EUROfusion and European incentive schemes for innovative investments. The project team includes more than 180 high-standard researchers from ENEA, CREATE, CNR, INFN, RFX and various universities. The volume, entitled DTT Interim Design Report (“Green Book” from the colour of the cover), briefly describes the status of the project, the planning of the design future activities and its organizational structure. The publication of the Green Book also provides an occasion for thorough discussions in the fusion community and a broad international collaboration on the DTT challenge

Development of a static shaft Wankel expander for small-scale applications

With increasing global demand for energy and the problems of climate change from extensive use of fossil fuels new ways to increase the renewable energy sources and reduce energy waste are required. Energy storage, such as liquid air energy storage (LAES), is one way to improve renewable energy utilisation. The organic Rankine cycle (ORC) is a system that allows the recovery of low-grade heat energy, which can be in the form of waste heat or geothermal heat. Both of these technologies are also good for distributed energy production, which reduces losses associated with energy transport. This thesis looks at the development of a Wankel gas expansion device for use in gas liquefaction or ORC systems. It starts with an extensive literature review into LAES and ORC systems. In which literature shows a clear need for the development of both gas liquefaction systems and small-scale, low-cost and efficient gas expanders. A review of available gas expanders is then presented followed by a detailed review of Wankel expansion devices. This review concludes that the Wankel expander has many qualities making it suitable for small-scale low-cost systems but has the issues of friction and the requirement for external valves which need to be addressed. The next part of the thesis describes the creation of numerical models to simulate gas liquefaction systems. The results of these models suggest that the Kapitza system performs the best, and the most effective way to increase its efficiency is improving the performance of the expansion device. Next, the creation of computational fluid dynamics (CFD) models for two different types of Wankel expander are described. One type is a standard Wankel expander with side ports, whilst the second is a newly designed static shaft Wankel expander based on the original DKM Wankel engine. The results of the CFD simulations show the main drawback of the standard Wankel expander is that it only reaches a maximum isentropic efficiency of 64.88%, due to lack of inlet control. The static shaft Wankel expander simulations show that it could reach isentropic efficiencies of 87.35% and can be designed for a large range of inlet pressures. CFD is also performed using two organic working fluids often used in organic Rankine cycle (ORC) systems, giving maximum isentropic efficiency of 85.6%. This demonstrates that the expander could be used in an ORC system and achieve similar performance to compressed air systems. Finally, an experimental test rig was designed and two static shaft Wankel expander prototypes were manufactured, one from plastic and one from metal. The prototypes were tested to find their power output and isentropic efficiency performances. Problems with the initial prototype design were found and a second prototype design was manufactured to address these issues. The experimental results were found to agree well with the CFD power output (average of 5.4W deviation), but with a much higher deviation for the CFD efficiency (average of 10.1% deviation), this was thought to be due to leakages not accounted for in the CFD models

Study of low grade temperature CCHP systems for the realization of zero power buildings

Combined Cooling Heat and Power Generation (CCHP) or trigeneration has been considered worldwide as a suitable alternative to traditional energy systems in terms of significant energy saving and environmental conservation. The development and evaluation of a solar driven micro-CCHP system based on a ORC cogenerator and an Adsorption Chiller (AC) experimental prototypes has been the focus of this PhD research. The specific objectives of the overall project are: • To design, construct and evaluate an innovative Adsorption Chiller in order to improve the performances of the AC technology. • To thermodynamically model the proposed micro-scale solar driven CHP system and to prove that the concept of trigeneration through solar energy combined with an organic Rankine turbine cycle (ORC) and an adsorption chiller (AC) is suitable for residential applications

Feasibility of residential solar air-conditioning in Australia, including space heating and hot water

In Australia residential air-conditioning has been claimed as one of the main drivers for peak electricity demand problems in the years from 2007 until 2012. Expensive network infrastructure upgrades have been required to maintain legislated reliability of electricity supply. This electricity grid augmentation has translated to increased cost of electricity for residences by around 70% until 2012 and 100% until 2014. This thesis investigates the potential for residential solar cooling to ease stress on the electricity grid while providing electricity cost savings to consumers and reductions in greenhouse gas emissions using a modeling approach. The modeling examines residential solar cooling performance in seven different climates in Australia, reviewing solar electric as well as solar thermal cooling options. Space heating and domestic hot water are included throughout this work. It strongly contributes to the cost-effectiveness of solar thermal systems and colder climates benefit most. The solar collector array for electricity and heat is sized to a cooling and heating solar fraction of 60%. In the first part of this work reference models are established to represent a residential building typical for each climate. In these models, the building is cooled and heated by a reverse cycle air-conditioner and domestic hot water is provided by a hot water system with an electric heating element. The first investigation involves addition of photovoltaic modules to offset grid electricity consumption of the reverse cycle air conditioner. In this configuration, the electricity grid acts as an energy supply buffer to supplement fluctuations in solar energy. The photovoltaic driven system design is very simple and proved to be the most cost-effective one. This investigation was extended to include options for electricity storage and a diesel electricity back up rather than the grid. The next investigation involved modeling a solar thermal system consisting of a single effect absorption chiller and an evacuated tube solar collector, following European examples. Initially, a sensitivity study was performed to better understand the model behavior and to size components correctly. The cooling system is scaled in a unique way to match the cooling load of each climate and to normalize energy consumption and cost. The absorption chiller uses gas as its backup energy source. The thermal solar cooling system model is extended by inclusion of options for a latent storage and a sensible chilled water storage tank. The results of the solar thermal system simulations are rather disheartening for the case of residential solar cooling using absorption chillers. Unless domestic hot water and space heating are included in the calculations, the levelized cost of space cooling and heating is too high to be acceptable when comparing it to the solar electric option. Including cold storage increases this cost even more, but additional greenhouse gases can be saved due to lower auxiliary gas consumption. The analysis would be expected to be different for large scale solar cooling installations, where absorption chillers can operate under base load conditions backed up by conventional chillers with good part load performance

Modelling of small capacity absorption chillers driven by solar thermal energy or waste heat

Aquesta recerca es centra en el desenvolupament de models en règim estacionari de màquines d’absorció de petita potència, els quals estan basats en dades altament fiables obtingudes en un banc d’assajos d’última tecnologia. Aquests models podran ser utilitzats en aplicacions de simulació, o bé per a desenvolupar estratègies de control de supervisió dels sistemes d’aire condicionat amb màquines d’absorció. Per tant, l’objectiu principal d’aquesta investigació és desenvolupar i descriure una metodologia comprensible i que englobi el procés sencer: tant els assajos, com la modelització, com també el desenvolupament d’una estratègia de control per a les màquines d’absorció de petita potència. Basant-se en la informació obtinguda de forma experimental en el banc d’assajos, s’han desenvolupat cinc models, cadascun amb una base teòrica diferent. Els resultats mostren que és possible obtenir models empírics summament precisos utilitzant únicament com a paràmetres d’entrada les variables dels circuits externs d’aigua. Aquest treball finalitza amb la proposta de dues estratègies òptimes de control i el seu ús per al control on-line de sistemes basats en refredadores tèrmiques d’absorció.This research deals with the development of the simple, yet accurate steady-state models of small capacity absorption machines which are based on highly reliable data obtained in the state-of-the-art test bench. These models can further be used in simulation tools or to develop supervisory control strategies for air-conditioning systems with absorption machines. Therefore, the main aim of this research is to develop and to describe a comprehensive methodology which encloses entire process which consists of testing, modelling and control strategy development of small capacity absorption machines. Five different models are developed based on the experimental data obtained in the test bench. The results show that it is possible to develop highly accurate empirical models by using only the variables of external water circuits as input parameters. Finally, two optimal control strategies are developed to demonstrate how these models can be used for on-line control of absorption systems