Abstract A continued increase in both energy demand and greenhouse gas emissions (GHGs) call for utilising energy sources effectively. In comparison with traditional energy set-ups, micro-combined heat and power (micro-CHP) generation is viewed as an effective alternative; the aforementioned system’s definite electrical and thermal generation may be attributed to an augmented energy efficiency, decreased capacity as well as GHGs percentage. In this regard, organic Rankine cycle (ORC) has gained increasing recognition as a system, which is capable for generating electrical power from solar-based, waste heat, or thermal energy sources of a lower quality, for instance, below 120 °C. This study focuses on investigating a solar-based micro-CHP system’s performance for use in residential buildings through utilising a regenerative ORC. The analysis will focus on modelling and simulation as well as optimisation of operating condition of several working fluids (WFs) in ORC in order to use a heat source with low-temperature derived from solar thermal collectors for both heat and power generation. A parametric study has been carried out in detail for analysing the effects of different WFs at varying temperatures and flowrates from hot and cold sources on system performance. Significant changes were revealed in the study’s outcomes regarding performance including efficiency as well as power obtained from the expander and generator, taking into account the different temperatures of hot and cold sources for each WF. Work extraction carried out by the expander and electrical power had a range suitable for residential building applications; this range was 0.5–5 kWe with up to 60% electrical isentropic efficiency and up to 8% cycle efficiency for 50–120 °C temperature from a hot source. The operation of WFs will occur in the hot source temperature range, allowing the usage of either solar flat plate or evacuated tube collectors.

A sodium thermal electrochemical converter (Na-TEC) converts heat directly into electricity without moving parts by isothermal expansion of ions through beta”-alumina solid-electrolyte (BASE). These generators are most similar to thermoelectric generators; however, they are considerably more efficient than the best performing thermoelectric materials. While these heat engines have been considered for CSP applications, literature review found that the efficiency of single-stage Na-TEC could readily achieve 20% even though ideal cycle efficiencies predict above 45% efficiency at elevated temperatures. Thermal parasitic loss has been identified to be responsible for the largest drop in the efficiency. Our recent study shows that staging helps to improve thermal management of the Na-TEC, due to the lower average temperature of the device, which can reduce the thermal parasitic loss. We demonstrate that dual-stage device can improve the efficiency by up to 8% over the best performing single-stage device. We are currently designing and developing a modular dual-stage Na-TEC power block with target efficiency of 33%. We emphasize modularity because this power block can be potentially deployed for both small-scale dish solar, which is appropriate for distributed residential scale (2–3 kWe), and large-scale heliostats and parabolic trough CSP, which is appropriate for centralized industrial scale. A fundamental cost-scaling relationship for this technology was developed based on this design. System variables and component manufacturing methods with material selection for processes were established. The current off-the-shelf component costs indicated an overnight capital cost of $2,044/kWe. The costs of BASE, manufacturing, and electrode preparation have driven the overall price of the module. The paper demonstrates $/W design optimization and cost scaling analysis to reduce the system capital $/W metric below $ 1,500/kWe, with the goal being to achieve the cost target of <900/kWe set by Department of Energy’s Sun Shot Initiative.

The main purpose of this study is to investigate the feasibility of using a hybrid photovoltaic (PV), fuel cell (FC) and battery system to power different load cases, which are intended to be used at Al-Zarqa governorate in Jordan. All aspects related to the potentials of solar energy in Al-Hashemeya area were studied. The irradiation levels were carefully identified and analyzed, and found to range between 4.1–7.6 kWh/m 2 /day; these values represented an excellent opportunity for the photovoltaic solar system. Various renewable and non-renewable energy sources, energy storage methods and their applicability regarding cost and performance are discussed, in which HOMER (Hybrid Optimization for Electric Renewable) software is used as a sizing and optimization tool. Different scenarios with Photovoltaic slope, diesel price, and fuel cell cost were done. A remote residential building, school and factory having an energy consumption of 31 kWh/day with a peak of 5.3 kW, 529 kWh/day with a maximum of 123 kW and 608 kWh/day with a maximum of 67 kW respectively, were considered as the case studies’ loads. It was found that the PV-diesel generator system with battery is the most suitable solution at present for the residential building case, while the PV-FC-diesel generator-electrolyzer hybrid system with battery suites best both the school and factory cases. The load profile for each case was found to have a substantial effect on how the system’s power produced a scheme. For the residential building, PV panels contributed by about 75% of the total power production, the contribution increased for the school case study to 96% and dropped for the factory case to almost 50%.

Traditional heat transfer techniques have become inadequate for many applications today and innovation of new technologies has become an urgent necessity. From another angle, securing electrical power remote areas in unconventional ways is receiving widespread attention. In this study, we present a new technique to dissipate heat, which is suitable in narrow and slanted places, as well as, generate electricity. The system consists of a permanent magnet (PM) and a spring where they act as opposing forces on a ferromagnetic disk moving in a specific space. Above the Curie temperature (Tc) of the ferromagnet, spring force (F spring ) overcomes the strength of the PM due to loss the magnetic susceptibility of the ferromagnet. PM’s force is gradually increasing and overcomes the F spring due to the cooling of the ferromagnetic. Thermally, the system consists of high and low temperature zones and the ferromagnetic works as an active heat carrier. The opposing forces of the PM and the spring make the ferromagnetic moves in two opposite directions. COMSOL Multiphysics 5.2a software is used to get the simulation results in this study. This technique is suitable for many applications especially when heat transfer is required in the horizontal or oblique direction. This technique provides clean energy using only a waste heat from anywhere as a source.

This paper proposes a new combined vibration suppressing device, which can be used to suppress the swaying vibration of off-shore floating wind generator under waves. The floating wind power station tower was modeled, the wave force and the torsion force of the tower were analyzed and the FSI numerical simulation was carried out. The calculation results demonstrate that the amplitudes of the tower torsion angle have been attenuated by 8%, 11% and 17% with different vibration suppression devices which are TMD, TLD and new combined device. In this case the new combined device has the best vibration suppression performance. It is validated that compared to the other two single vibration suppression devices, the new combined device has better vibration suppression capacity and a new way is provided to design the vibration suppression device for off shore floating wind power station.

From a practical perspective, economics drive the development of distributed energy resource (DER) systems. However, the adoption of a DER system provides an opportunity for the end user to completely control their environmental footprint. This work examines the process of designing a DER system while controlling carbon emissions. A mixed integer linear program (MILP) for sizing and dispatching a DER system is developed. The MILP includes a novel formulation of constraints that govern utility natural gas, generator operational state, and charging of thermal energy storage. The MILP is executed using real energy demand data for the University of California, Irvine to optimally design a DER system that minimizes cost while also reducing carbon emissions by a specified quantity. Two primary technology scenarios are explored (DER including storage with and without electrical export). A trajectory of DER technology adoption is determined for both technology scenarios. The different operational methods through which each system achieved lower carbon emissions at minimum cost is examined. Finally, the cost to reduce carbon emissions is calculated for both technology scenarios.

The use of pumps as turbines (PAT) has gained importance in the recent years as a possible alternative to specifically developed turbine for mini/micro hydropower plants. The use of production pump for hydropower generation reduces the capital cost of the plant but the energy conversion efficiency can be remarkably lower. The paper analyses the performance of a production centrifugal pump running both in direct and reverse mode. The analysis calculates theoretically the behavior of the PAT under the best efficiency point and extends the investigation to other operating points using both a combined theoretical approach and CFD simulation under dynamic conditions. The effects of possible modifications to the initial design of the pump are investigated when running in turbine mode and their influence on the standard pump operation is also determined. Numerical simulation demonstrates that the impeller trimming leads to improvement in the PAT efficiency in some operating conditions. Conversely, the rotational speeds close to the values typical for the electric generator reduce the PAT performance. Finally, the modification of the impeller geometry at the turbine inlet increases the PAT efficiency but lowers the performance of the machine when running in pump mode.

In this paper, a numerical simulation of tether undersea kites (TUSK) used for power generation is undertaken. The effect of varying key design parameters in these systems is studied. TUSK systems consist of a rigid-winged kite, or glider, moving in an ocean current. One proposed TUSK concept uses a tethered kite which is connected by a flexible tether to a support structure with a generator on a surface buoy. The numerical simulation models the flow field in a three-dimensional domain near the rigid undersea kite wing by solving the full Navier-Stokes equations. A moving computational domain method is used to reduce the computational run times. A second-order corrector-predictor method, along with Open Multi-Processing (OpenMP), is employed to solve the flow equations. In order to track the rigid kite, which is a rectangular planform wing with a NACA 0021 airfoil, an immersed boundary method is used. The tension force in the elastic tether is modeled by a simple Hooke’s law, and the effect of tether damping is added. PID control methods are used to adjust the kite pitch, roll and yaw angles during power (tether reel-out) and retraction (reel-in) phases to obtain the desired kite trajectories. During the reel-out phase the kite moves in successive cross-current motions in a figure-8 pattern, the tether length increases and power is generated. During reel-in the kite motion is along the tether, and kite hydrodynamic forces are reduced so that net positive power is produced. The effects of different key design parameters in TUSK systems, such as the ratio of tether to current velocity, and tether retraction velocity, are then further studied. System power output, kite trajectories, and vorticity flow fields for the kite are also determined.

Increasing grid penetration of intermittent renewable power from wind and solar is creating challenges for the power industry. There are times when generation from these intermittent sources needs to be constrained due to power transmission capacity limits, and times when fossil fuel power plant are required to rapidly compensate for large power fluctuations, for example clouds pass over a solar field or the wind stops blowing. There have been many proposals, and some actual projects, to store surplus power from intermittent renewable power in some form or other for later use: Batteries, Compressed Air Energy Storage (CAES), Liquid Air Energy Storage (LAES), heat storage and Hydrogen being the main alternatives considered. These technologies will allow power generation during low periods of wind and solar power, using separate discrete power generation plant with specifically designed generator sets. But these systems are time-limited so at some point, if intermittent renewable power generation does not return to its previous high levels, fossil fuel power generation, usually from a large centralized power plant, will be required to ensure security of supplies. The overall complexity of such a solution to ensure secure power supplies leads to high capital costs, power transmission issues and potentially increased carbon emissions to atmosphere from the need to keep fossil fuel plant operating at low loads to ensure rapid response. One possible solution is to combine intermittent renewables and energy storage technologies with fast responding, flexible natural gas-fired gas turbines to create a reliable, secure, low carbon, decentralized power plant. This paper considers some hybrid power plant designs that could combine storage technologies and gas turbines in a single location to maximize clean energy production and reduce CO 2 emissions while still providing secure supplies, but with the flexibility that today’s grid operators require.

Successful deployment of large amounts of renewable solar and wind energy has created a pressing need for significant additions of grid connected energy storage. Excess renewable generation is increasingly necessitating curtailment or derating of renewable or conventional generators. The CAISO Duck Curve [8] illustrates the challenge caused by very large quantities of solar generation. Both large scale energy storage and flexible ramping are needed for renewable resources to be financially sustainable and to meet CO 2 reduction goals. The Dispatchable Solar Combined Cycle (DSCC) integrates Concentrating Solar Power (CSP) with Thermal Energy Storage (TES) in a holistic combined cycle configuration to meet the challenges of the CAISO Duck Curve by delivering flexible capacity with dispatchable solar power. Energy cost from DSCC is comparable to that from a Combined Cycle Power Plant (CCPP), and substantially below the alternatives: Photovoltaic plus battery or Photovoltaic plus combustion turbine. DSCC also enable far higher integration of renewable power and far larger renewable capacity factors than the Integrated Solar Combined Cycle (ISCC), which typically has no storage. The innovative DSCC system: • uses energy storage to deliver power when it is most valuable, • increases the capacity factor to deliver more renewable energy, • improves the power plant Heat Rate to reduce fuel consumption, and • reduces the cost of power while addressing RPS and storage mandates. In DSCC, the CSP and TES are used primarily for latent heat: the evaporation of steam, and the Combustion Turbine (CT) exhaust gas is used primarily for sensible heating, especially superheating steam. This simplifies the integration of low-cost storage media, such as paraffinic oils or concrete, instead of molten salt, since high temperature storage is not needed. A single pressure, non-reheat steam cycle suitable, allowing for simplicity of design and operation, reducing costs and facilitating faster startup and ramping. With DSCC, the steam turbine generates about the same power as the CT, unlike a typical CCPP where about half the power comes from the steam cycle. The additional steam production reduces the Heat Rate about 25% compared to CCPP. The DSCC approach is ideally suited for repowering existing CSP plants, to provide firm capacity that can dispatch at valuable evening peak periods, increase the power output, and reduce fossil fuel use compared with conventional CCPP or peaking plants. This paper will outline the DSCC concept, and provide performance estimates for a reference plant.

In this work an emerging hydrokinetic energy technology, Tethered UnderSea Kites (TUSK), is studied. TUSK systems use an axial-flow turbine and generator mounted on a rigid, underwater winged kite that is tethered to a floating surface buoy to extract power from an ocean current. The tethered underwater kite is controlled to travel in cross-current motions at a high velocity which is at least four to five times larger than the ocean current velocity. This higher velocity significantly increases the potential power output compared to conventional fixed marine turbines. Modeling and simulation of the kite-tether dynamics in a TUSK system is studied by developing and solving governing equations of motion derived from Euler-Lagrange equations. Models for physical effects appropriate to TUSK systems are developed, including for turbine power and turbine drag, kite wing hydrodynamic forces, and the effect of turbine blade tip cavitation on turbine power output. A baseline simulation that includes these modeled effects and a simple kite control scheme is studied to estimate cross-current kite trajectories, turbine power output, kite hydrodynamic forces, kite pitch, roll and yaw dynamics, and tether tensions. Once the baseline simulation case has been fully explored, a parametric study is conducted that varies key design and flow parameters including ocean current speed, kite weight and wing area, turbine rotor area, tether length, and kite control system parameters.

Current trends show that renewable energy production costs continue to decrease with time, so that renewable energy sources (RES) are becoming more suitable as electricity sources. In addition to their environmental benefits, RES are especially appropriate for remote areas, where the expansion of existing power grid is impractical and fuel transportation for thermal generators is too expensive. In this regard, our work studies the optimal capacity sizing for a completely green village (CGV), which is an isolated residential microgrid (MG) whose power is entirely generated by RES. In particular, we consider a neighborhood composed of smart homes that contain programmable appliances, whose operations can be interrupted or automatically scheduled in time. Though there are many works in literature that investigate MG optimal capacity sizing, to our knowledge, our work is the first that utilizes the scheduling of programmable appliance to minimize MG investment costs. To establish the effectiveness of our method, we compare an optimal MG capacity sizing algorithm that utilizes appliances’ programmability (Opt-P) with an algorithm that places appliances into operation as soon as they are ready without shifting in time or preempting their operation (NoSch-P). Our simulation results show that Opt-P reduces the investment cost by at least 42% compared to NoSch-P, when the ratio between the energy storage investment cost per kWh and the RES’ investment cost per kW is greater or equal to 10.

In order to reduce the quantity of CO 2 emissions economically, it is important to construct a Smart Community which is expected to be one of the solutions. In a Smart Community, energy supply and demand system is developing to manage with ICT (Information and Communication Technology) to utilize energy efficiently and increase the amount of renewable energy. In one of the systems, “Photovoltaic power generator (hereinafter referred to as PV) & Electric Vehicle (hereinafter referred to as EV) Smart System” has been developed. In the “PV & EV Smart System”, PV power is charged directly to the EV battery, and then the charged PV power is consumed by running and air-conditioning energy of a car and supplied to a home. This system is able to reduce the quantity of CO 2 emissions with high economic efficiency. In order to expand the system, it is necessary to spread EV. So, it should solve the issues of short driving distance, the high cost of storage battery and the risk of dead battery. Therefore, the authors have proposed an advanced EV such as AI-EV (Air-conditioner Integrated Electric Vehicle). AI-EV has a novel hybrid system which drives the air-conditioning system and generates electric power in the case of a low air-conditioning load through the use of a small-engine. PV power can not only reduce car fuels but also replace with gas and liquid fuels which are used at a home, causing the huge effect of reducing CO 2 emissions as the whole system. In this paper, a novel energy system which is integrated with solar power, advanced electric vehicle and CO 2 heat pump water heater as home heat pumps has been proposed. A mathematical simulation model which evaluates for the PV power generation, AI-EV energy consumption and home heat pumps has been developed. CO 2 emissions and economic efficiency are calculated and compared with those of the conventional system. As the result, the novel energy system is able to reduce more than 30% of the quantity of CO 2 emissions in comparison with the conventional system as the whole system, and the system can reduce about 60% of the quantity of CO 2 emissions in comparison with the conventional system as a home system. The economic efficiency is evaluated by more than 6.0% of IRR (Internal Rate of Return) without some subsidies when the legal service life of the depreciation equipment is assumed 14 years. Therefore, the novel energy system can be widely spread in the future.

The process of generating electricity using solar energy took a great interest in the recent period for its contribution to the reduction of the fossil fuel consumption and the harmful emissions to the environment. The main task of this article is to simulate the thermal performance of a solar power plant for electricity production using a parabolic trough concentrator for accumulating the solar heat. The plant includes a stratified storage tank, steam generator, steam turbine and an electric generator. The simulation studies the effect of the design parameters of the solar field and the storage tank on the annual performance of a 1 MWe solar electric power plant. The simulation platform TRNSYS was used to model the solar power plant including the solar concentrator field, the storage tank, and the steam generator. The simulation predicts the instantaneous and annual heat energy collected by the solar concentrator and the heat energy rate supplied, extracted, and stored in the storage tank. It predicts also the rate and the quality of the steam produced. This analysis was applied to four sites in Egypt to study the effect of the solar radiation on the energy produced in those sites.

Net metering is an incentive that is essential to most solar photovoltaic systems. Recently the burden placed upon local utilities is an issue some regulators have been asked to address. This research uses actual 2013 and 2014 solar production data from nearly 200 sites, wholesale electricity day-ahead pricing data, and utility-wide demand data. This is all analyzed by the hour for two full years for a western Pennsylvania based utility and an eastern Pennsylvania based utility and their wholesale generators. Results show electricity is 15% more valuable when solar PV systems are generating power and feeding the grid during good weather conditions than at night or cloudy days when solar customers get energy back from the grid. Solar energy generation is highly predictable in the day-ahead market, and leads to suppression in market prices for electricity. Thus to reveal the true impact of this market suppression, an increased solar renewable portfolio standard (RPS) fraction of 0.2 to 10% was simulated. This caused a decrease in demand resulting in a corresponding reduction in the price of electricity yielding savings to the utility. The maximum rate of increase and decrease in the utility-wide load did not change significantly until the solar RPS exceeded 5%. Additionally, the demand for electricity was reduced during the highest load hours of the year that corresponded to the most expensive hours of the year. The minimum base-load of the year was decreased substantially for solar RPS of 5% or greater and the base load reaches zero for solar RPS over 10%. From the data of these two years, it is demonstrated that an increased use of solar energy would lead to savings that are larger than the loss in revenue due to having fewer traditional non-solar customers. Thus electricity suppliers and utilities stand to have both higher profits and higher profit margins when customers adopt net-metered solar energy compared to the non-adoption of solar energy.

Integration of non-dispatchable renewable energy sources such as wind and solar into the grid is challenging due to the stochastic nature of energy sources. Hence, electrical hubs (EH) and virtual power plants that combine non-dispatchable energy sources, energy storage and dispatchable energy sources such as internal combustion generators and micro gas turbines are getting popular. However, designing such energy systems considering the electricity demand of a neighborhood, curtailments for grid interactions and real time pricing (RTP) of the main utility grid (MUG) is a difficult exercise. Seasonal and hourly variation of electricity demand, potential for each non-dispatchable energy source and RTP of MUG needs to be considered when designing the energy system. Representation of dispatch strategy plays a major role in this process where simultaneous optimization of system design and dispatch strategy is required. This study presents a bi-level dispatch strategy based on reinforced learning for simultaneous optimization of system design and operation strategy of an EH. Artificial Neural Network (ANN) was combined with a finite state controller to obtain the operating state of the system. Pareto optimization is conducted considering, lifecycle cost and system autonomy to obtain optimum system design using evolutionary algorithm.

The importance of integrating renewable energy sources into standalone energy systems is highlighted in recent literature. Maintaining energy efficiency is challenging in designing such hybrid energy systems (HES) due to seasonal variation of renewable energy potential. This study evaluates the limitations in minimizing the losses in renewable energy generated mainly due to energy storage limitations and minimizing fuel consumption of the internal combustion generator (ICG). A standalone hybrid energy system with Solar PV (SPV), wind, battery bank and an ICG is modeled and optimized in this work. Levelized Energy Cost (LEC), Waste of Renewable Energy (WRE) and Fuel Consumption (FC) are taken as objective functions. Results highlight the importance of considering WRE as an objective function which increase the mix of energy sources that can help to increase the reliability of the system.

Bi-directional turbines convert oscillating axial fluid flow into uniform radial rotation and have proven effective in wave energy harvesting applications, like ocean wave generators. Two of the most widely studied designs for these scenarios are the Wells and axial turbines. This study characterizes the effectiveness of these turbines for use with a thermoacoustic generator; which is a relatively new technology that uses an induced temperature gradient to propagate acoustic waves within an enclosed, looped chamber. These generators are widely applied to refrigeration cycle systems; yet when paired with a bi-directional turbine, the resulting sound wave can be harnessed to generate electricity. This paper begins with a discussion of the thermoacoustic application covering relevant issues for the turbine. Next, the Wells, axial, and a combined hybrid turbine are presented in thorough detail including governing design features that were explored. Fabrication of a test fixture and turbine prototypes and experimental results from a broad ranging study of the performance of the turbine designs is shown. Finally, conclusions from the obtained results are discussed.

Germany’s current energy policy is focused on the replacement of the conventional powered electrical energy supply system by renewable sources. This leads to increasing requirements on the flexibility for the conventional thermal power plants. Larger differences between energy supply from renewable energy sources and energy demand in the grid lead to high dynamic requirements with respect to the load change transients. Furthermore, a reduction of the required minimum load of existing thermal power plants is necessary. The existing power plants are indispensable for securing the network stability of the power grid. Accordingly, activities to improve the flexibility of existing power plants are required. By the use of thermal energy storage (TES) it is possible to increase the load change transient. Furthermore, it is possible to temporarily provide an increased generator power and reduce the minimum technical load of the unit. Currently, there is no closed methodical approach for the load profile-dependent and location-based dimensioning and integration of TES into thermal power plants. The aim is to generate contributions for the development of a universal design method. This requires the provision of characteristics for dimensioning and integration of TES into thermal processes. For this purpose, it is necessary to derive quantifiable information on the required capacity, performance and stationary and dynamic operating conditions. Starting from analyzing the anticipated, site-specific load profiles the derivation of concepts for technical implementation, feedback on the process and cost of the thermal storage unit takes place. In order to investigate the technical feasibility, the implementation of storage and the associated control concepts as well as to validate the developed design models, the test facility THERESA has been built at the University of Applied Sciences in Zittau (Germany). The acronym THERESA is the abbreviation for thermal energy storage facility. This test facility includes a reconstructed thermal water-steam process, similar to a power plant with integrated TES. The test facility is unique in Germany and enables the delivery of saturated steam up to 160 bars at 347 ° and superheated steam up to 60 bars at 350 °C with an overall thermal power of 640 kW. The design, planning and construction of the facility took 3 years and required an investment volume of 3 mill. Euro. The facility includes two preheater stages, steam generator, super heater, direct TES with mixing preheater and a heat sink. The TES with a volume of 600 L as well as the mixing preheater are prototypes which developed for the special requirements of the facility. Based on this facility, it is possible to investigate methods for the flexibilization of thermal power plants with TES under realistic parameters. Furthermore, the test facility allows the development of control and regulatory approaches as well as the validation of simulation models for process expansion of thermal power plants. Initial investigations show the impact of a simulated load reduction at the heat sink on the system behavior. Here, the load reduction takes place from the heat sink in the storage without changing the steam production. The development and construction of the test facility were funded by the Free State of Saxony and the European Union. The further work on the development of the integration methods are funded by the European Social Fund ESF.

This presentation will discuss the results of the feasibility analysis of a Brayton cycle-based, supercritical CO 2 system that recovers waste heat from an MT30 gas turbine used in marine applications. The analysis also included the use of thermoelectric generator (TEG) devices that are one of several direct energy conversion methods known to be applicable to waste heat recovery. The analysis was conducted by Concepts NREC, in collaboration with the Maine Maritime Academy and their principal consultant, Thermoelectric Power Systems, LLC. The feasibility analysis was conducted under Navy SBIR Proposal Number N103-229-0533, entitled “Gas Turbine Engine Exhaust Waste Heat Recovery Shipboard Module Development”. The objective of the project was to improve the energy efficiency of the MT30 prime-mover power system for the Navy and other commercial vessels. The performance goal for the energy recovery system was to improve the fuel economy of the prime mover by 20% when significantly part-loaded.