Fuel cell-based cogeneration system covering data centers’ energy needs

The Information and Communication Technology industry has gone in the recent years through a dramatic expansion, driven by many new online (local and remote) applications and services. Such growth has obviously triggered an equally remarkable growth in energy consumption by data centers, which require huge amounts of power not only for IT devices, but also for power distribution units and for air-conditioning systems needed to cool the IT equipment. This paper is dedicated to the economic and energy performance assessment of a cogeneration system based on a natural gas membrane steam reformer producing a pure hydrogen flow for electric power generation in a polymer electrolyte membrane fuel cell. Heat is recovered from both the reforming unit and the fuel cell in order to supply the needs of an office building located near the data center. In this case, the cooling energy needs of the data center are covered by means of a vapor-compression chiller equipped with a free-cooling unit. Since the fuel cell’s output is direct current rather than alternate current, the possibility of further improving data centers’ energy efficiency adopting DC-powered data center equipment is also discussed

Hybrid fuel cell-based energy system with metal hydride hydrogen storage for small mobile applications

This paper describes the general architecture of a hybrid energy system, whose main components are a proton exchange membrane fuel cell, a battery pack and an ultracapacitor pack as power sources, and metal hydride canisters as energy storage devices, suitable for supplying power to small mobile non-automotive devices in a flexible and variable way. The first experimental results carried out on a system prototype are described, showing that the extra components, required in order to manage the hybrid system, do not remarkably affect the overall system efficiency, which is always higher than 36% in all the test configurations examined. in fact, the system allows the fuel cell to work most often at quasi-optimal conditions, near its maximum efficiency (i.e. at low/medium loads), because high external loads are met by the combined effort of the fuel cell and the ultracapacitors. For the same reason, the metal hydride storage system can be used also under highly dynamic operating conditions, notwithstanding its usually poor kinetic performance. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved

Fuel cell-based cogeneration system covering data centers' energy needs

The Information and Communication Technology industry has gone in the recent years through a dramatic expansion, driven by many new online (local and remote) applications and services. Such growth has obviously triggered an equally remarkable growth in energy consumption by data centers, which require huge amounts of power not only for IT devices, but also for power distribution units and for air-conditioning systems needed to cool the IT equipment. Following a previous work where the authors analyzed energy and cost savings that could be achieved in the energy management of data centers by means of a conventional combined cooling, heating and power system based on an internal combustion engine and a LiBr/H2O absorption chiller, this paper is dedicated to the economic and energy performance assessment of a CHP system based on a natural gas membrane steam reformer producing a pure hydrogen flow for electric power generation in a polymer electrolyte membrane fuel cell (PEMFC). Heat is recovered from both the reforming unit and the fuel cell in order to supply the needs of an office building located near the data center. In this case, the cooling energy needs of the data center are covered by means of a vapor-compression chiller equipped with a free-cooling unit. Since the fuel cell’s output is direct current (DC), rather than alternate current (AC) as in electric generators driven by internal combustion engines, the possibility of further improving data center’s energy efficiency by the adoption of DC-powered data center equipment is also discussed

Kinetic energy recovery system for sailing yachts

SEAKERS (SEA Kinetic Energy Recovery System) is a research project, funded within the 7th EU Framework Programme and officially started on January 1st, 2011, whose goal is to develop an innovative device consisting in a kinetic energy recovery system for sailing yachts based on the conversion of boat oscillations (heave, pitch and roll) caused by the sea into electric energy by means of a linear generator. Therefore, SEAKERS addresses a well known unsatisfied requirement of yacht owners, since energy is a resource of primary importance in a boat, especially in a sailing one: it is well known that during a one day cruise, electricity consumption has to be carefully managed (for instance the refrigerator is switched off), so as not to be short of energy at night. It often happens that, after one day of sail cruise, it is necessary to recharge the batteries through the onboard generator, which means keeping it on for hours, producing very annoying noise, smoke and pollution. The device that is going to be developed aims at recovering as much kinetic energy as possible from the natural movements of a sailing yacht on the sea, therefore taking the view of a boat as a moving wave energy converter with energy harvesting capacity. The boat’s motions can be vertical oscillations due to the buoyancy in the presence of sea waves, both when the boat is still or sailing, and rolling and pitching motions originated both by sailing in wavy waters and by the normal boat dynamics due to the sails’ propulsion. Linear generators will convert kinetic energy into electrical energy to be used as “green” electricity for any possible application on board. Preliminary calculations show that a properly configured system could be able to recover 100-400 W under most sea conditions, which can be an extremely attractive result since an electric energy availability of 1-2 kWh on a sailing yacht is of significant interest

The effects of incondensable gases on H2/O2 cycle performance

In this paper a method to evaluate the expansion of condensing steam in presence of incondensable gases is presented. The expansion of such a mixture involves thermodynamic processes very different from those related to the expansion of pure steam (as it happens in conventional steam power plants) or to the expansion of a gaseous mixture without steam condensation (as it happens in gas turbine power plants, combined and mixed cycles). In this paper these thermodynamic processes are investigated and an evaluating method is developed. In particular using this method it is possible to evaluate the excess turbine back pressure, that is the pressure increase with respect to the steam saturation pressure, and the specific expansion work of the mixture. The proposed method is then applied in order to evaluate the performance of an hydrogen/oxygen (fuel/oxidiser) cycle, where the presence of incondensable gases into condensing steam is unavoidable owing to the processes that give H2 from fossil fuels and O2 from air. The results of the developed investigation confirm that the presence of incondensable gases can not be neglected for a realistic evaluation of H2/O2 cycle performance

New high efficiency mixed cycles with air-blown combustion for CO2 emission abatement

In this paper a new advanced mixed cycle (AMC) for CO2 emission abatement with high conversion efficiency is presented. The AMC plant lay-out consists of a reheat gas turbine with steam injection in the first combustion chamber, a steam turbine for steam expansion before its injection, a heat recovery boiler for superheated and resuperheated steam generation and an atmospheric separator for water recovery from exhaust gas mixture. The steam recirculation in the cycle allows to reduce the excess of air to limit the turbine inlet temperature and then to enrich the exhaust gas by CO2, as it occurs in combined cycle provided with exhaust gas recirculation at the compressor inlet. This involves a stack flow rate much lower than in conventional cycle configuration so that exhaust gas treatment for CO2 removal may be useful applied. In this work the chemical absorption technique for CO2 removal has been considered. The thermodynamic performance of the proposed AMC plant has been investigated in comparison with that attainable by combined cycle power plants (CC). This comparison has been developed pointing out the efficiency decrease involved by the CO2 removal systems and by the unit for the liquefaction of the removed carbon dioxide. The main result of the performed investigation is that while the two plants attain the same efficiency level without CO2 removal (about 56% for AMC and 55.8% for CC) the AMC plant achieves a net electric efficiency of about 50% with CO2 removal and liquefaction units: it's over 2 points higher than the efficiency evaluated for the CC equipped with the same CO2 units (about 47.7%). The final carbon dioxide emissions are resulted of about 0.04 kg/kWh for AMC and CC, while the emissions of the plants without CO2 removal systems are of about 0.36 kg/kWh

Intermittent non-dispatchable renewable generation and reserve requirements: historical analysis and preliminary evaluations on the Italian electric grid

Intermittent renewable generators, mostly solar photovoltaic (PV) and wind power plants (W), have been growing across the Italian electric grid at an unprecedented rate over the last years. At the beginning of 2013, GSE (state-owned company supporting renewable energy sources) surveyed 16,4 GW of installed PV systems and 8,1 GW of wind farms, covering a significant share of Italian electric demand, which has been ranging between 21 GW and 54 GW over the same year. Such a relevant amount of installed intermittent power generators, fostered by priority dispatch, has already had relevant effects on the electricity market, in both its two components: the energy market (MGP) since the end of 2013 has been steadily lowering its single national purchase price (PUN), even recording zero purchase prices; at the same time, the amount of resources needed to establish reserve margin on the dispatching services market (MDS) has increased, due to a growing amount of intermittent generators penetrating on the grid, at a yearly rate of 5%, as shown from our historical analysis. A preliminary evaluation method of reserve requirements was developed taking into account forecast variability in electric load and intermittent renewable generation. The model was used to evaluate the growth of reserve requirements with an expected larger share of renewable generators. The magnitude of this relevant parameter was assessed, thus estimating the addressable penetration of energy storage systems and virtual power plant needed to overcome renewable intermittency

Advanced H2/air cycles based on coal gasification

In this paper the overall performance of a new advanced mixed cycle (AMC), fed by hydrogen-rich fuel gas, has been evaluated. Obviously, hydrogen must be produced and here we have chosen the coal gasification for its production, quantifying all the thermal and electric requirements. At first, the thermodynamic performance of this cycle has been investigated in comparison with that attainable by combined cycle power plants (CC). Then, the power plants have been integrated with the fuel production system. Including all the material and energy flows, the overall performance has been evaluated. The main result of the performed investigation is that the two power plants attain the same efficiency level with and without H2 production requirements (over 60% and over 34% without and with hydrogen production respectively). The final carbon dioxide emissions are about 0.123 kg/kWh both for AMC and CC. It is important to underline that the "clean" use of coal in new power plant types must be properly investigated because it is the most abundant and the cheapest fossil fuel available on earth; moreover, hydrogen production, by using coal, is an interesting prospect because hydrogen has the potential to become the main energy carrier in a future sustainable energy economy

Comparative analysis of combined cooling, heating and power systems (CCHP) covering data centers energy needs

The Information and Communication Technology (IT) industry has gone in recent years through a dramatic expansion, driven by many new applications and services available on private or public networks. Such growth has obviously needed an equally remarkable growth in energy consumption by data centers, which require huge amounts of power not only for IT devices (servers, network equipment, storage devices), but also for power distribution units (including uninterruptible power sources) and for ventilation and conditioning. It is reasonable to expect that such growth trend will continue in the forthcoming years, given the ever increasingly important role that is being played by IT-related applications and services. It is therefore of the utmost importance to assess the energy consumption of data centers in order to devise possible ways to increase energy efficiency, because in a conventional data center the cooling and power distribution equipment can absorb the same power as the IT equipment itself. An interesting option is the use of distributed generation and combined cooling, heating and power systems (CCHP) designed to meet the whole energy needs of data centers, with absorption chillers used to recover heat discharged by a thermal engine (internal combustion engine or gas micro-turbine) or a fuel cell. Indeed, this would be an almost ideal application of trigeneration, given that electric and cooling power are always required simultaneously, and are not subject to significant daily or seasonal oscillations (with the result of very high utilization factors). Under these circumstances, trigeneration systems can produce relevant benefits for the environment, through reduced primary energy consumption and greenhouse gas emissions, and for data center managers as well, through cost savings related to “lighter” energy bills. In this paper a study is presented offering a comparative analysis of the performance of state-of-the-art trigeneration technologies. In particular, the study compares the energy performance of a conventional data center with the results that can be achieved by generating electric energy by means of CCHP systems based on internal combustion engines and LiBr/H2O absorption chillers. The main results are presented in terms of reduction of primary energy consumption, of greenhouse gas emissions and of annual data center operating costs