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The road to accelerator energy efficiency

Jennifer Toes — Tue, 04 Jul 2017 09:17:20 +0000

The road to accelerator energy efficiency

by Jennifer Toes (CERN)

Construction at CERN of a prototype of a 144:1 power combiner to combine 144 solid-state amplifiers
of 1 kW each (Image: Eric Montesinos)

As accelerators change, grow and advance to continue to make scientific discoveries, so too does their need for energy.

Keeping particle accelerators sustainable, minimising their cost and impact on the public energy grid and environment, is a current goal for many particle physicists and engineers. Work Package 3 (WP3) of the EuCARD-2 project, which ended in April 2017, produced a dedicated report on maximising the energy efficiency of certain accelerator systems and alternate uses for energy wasted in the form of heat.

Radiofrequency (RF) systems, commonly used in accelerators to drive accelerating structures in accelerating particles, are prone to energy wastage and often contribute to the overall energy inefficiency of accelerator facilities. As such, WP3’s Task 3 reviewed concepts and designs for more efficient RF systems, whilst Task 2 investigated avenues for making use of or recovering lost energy by other means.

When considering more efficient RF systems, Task 3 focused on supporting the development of three technologies: 1) multi-beam Inductive Output Tubes (IOTs), 2) an improved bunching mechanism for klystrons, and 3) efficient power combiners for use with solid-state power amplifiers in large accelerators.

Compared to klystrons, IOTs have lower losses of energy between pulses or at low input power. However, klystrons may still be improved with new bunching schemes which would extract the RF power from accelerated electron beams more efficiently. In addition, solid state amplifiers can be realised using a single state power combiner, which combine a large number of transistors for higher RF power.

Whilst minimising the initial energy waste is important, so too is identifying how to recover wasted energy, or how to repurpose potential waste for other uses.

Mike Seidel, WP3 Coordinator and head of Accelerator Operation and Development at the Paul Scherrer Institute (PSI), commented, “Energy efficiency and sustainability is becoming an important consideration for modern accelerator based research infrastructures. During EuCARD-2 we found that even matured technologies, such as klystrons, have significant potential for efficiency improvements. At large facilities wasted energy can be used very beneficially for heating purposes, and as the example of ESS shows, the best concepts can be realised if these are included in the planning of a project from the very beginning.”

The members of WP3 Task 2 surveyed 12 accelerator facilities from seven different European countries on their energy consumption and cost as well as cooling and heat recovery methods. The task aimed to obtain an overall understanding of the energy consumption in accelerator facilities and identify beneficial aspects of various set-ups as well as areas requiring improvement.

Both RF and cryogenic systems (the latter of which uses very low temperature liquids for cooling) contribute large levels of energy wastage in the form of heat. Recovering this heat or harnessing its power for additional applications, such as heating treating wastewater, may help further efficiency efforts.

WP3 has identified the need to develop new technology, improve current systems, and pursue methods to recover or repurpose lost energy to ensure the particle accelerators of tomorrow are as efficient as possible.

EuCARD-2

energy

energy efficiency

heat recovery

radiofrequency

issue 21

Accelerators for testing energy efficiency

Panagiotis Charitos — Mon, 06 Mar 2017 13:11:24 +0000

Accelerators for testing energy efficiency
by Jennifer Toes (CERN)

3D Photo Composition of the Planned FAIR Facility at GSI (Image: FAIR/Jan Schäfer)

Researchers at GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany have presented preliminary results for the integration of accelerator facilities into Virtual Power Plant (VPP) networks within the scope of the EuCARD-2 project.

Virtual Power Plants (VPPs) are networks that aim to optimise the production, storage and use of energy. They are comprised of renewable producers such a wind turbines and solar panels, storage facilities such as battery stations, and both public and industrial users. The networks aim to ensure better availability and reliability for consumers.

Dr Jens Stadlmann, Vice Machine Coordinator of SIS18 at GSI, said: “Accelerators are large and variable power consumers which makes them eligible candidates for VPP.”

The GSI team analysed the energy consumption of the accelerator complex and found a 3-6 MW difference between operation and shutdown. This meant the shutdown of the equipment could be scheduled during times of high-energy demand by identifying switchable loads.

The FAIR Facility

In an effort to consider the feasibility for future accelerator complexes, the GSI team studied the SIS100, the main synchrotron of the future Facility for Antiproton and Ion Research (FAIR).

The FAIR synchrotron will be able to work in very flexible cycles with three different modes of operation: Cycles A, B and C. Cycles A and B are regular modes of operation, which have similar dynamic loads and safety margins but Cycle C has much higher dynamic loss and is not planned as a regular mode of operation.

Experiments could schedule operation cycles with high dynamic loss around times of low energy demand. Next, power providers could make use of the whole facility as part of a VPP scenario by actively switching accelerator facilities to a low energy consuming cycle when general power demand is high.

Challenges for accelerators in VPP networks

Potential energy management schedules for accelerators must be considered carefully, as researchers may be expected to wait significant periods for the facility to be switched back to high-energy operation. Longer operating times may be required to compensate, which has its own impact on energy consumption and staff and operating costs.

In addition, the operation of the cryogenic system during low-energy may present a technical challenge for facility operators.

The SIS100 magnets are cooled by a two-phase helium system, whereby liquid helium extracts heat from the magnets and is evaporated back into a gas before being transported back to the surface of the facility.

If an accelerator facility is switched to low-energy operation, the level of cooling must be adjusted accordingly. At a lower energy magnets will produce less heat, so not all of the liquefied helium can be evaporated.

To recoup all of the deployed helium, facilities may need to install heaters or a method of pumping the liquid back into the feed box. Using heaters means the energy consumption of the cryo plant will stay relatively constant for all modes of accelerator operation. Significant changes must be made at the cryosystem to realise lower energy consumption during cycles of low dynamic load.

Next steps for accelerators and VPPs

Allowing power suppliers to switch accelerator facilities from high to low energy during times of high energy demand adds a layer of complexity and risk to facility operation.

Before accelerators may be fully integrated into VPP networks the cryogenic systems require further development, safety measures must be assessed and the facility must comply with additional regulations from the power network operators.

The longer operating times needed to compensate users for a loss of beam time may result in similar or higher energy consumption, and the costs for the manpower and operation of these facilities may also be higher.

Trialling for the expansion of VPP networks with accelerator facilities may allow researchers and power suppliers to identify potential obstacles to further use, which in turn may present future avenues of research and development.

“The technical and organisational obstacles which have to be overcome to qualify a complex machine like an accelerator for a VPP seem to be transferable to other scenarios und thus be of general interest for society,” said Dr Stadlmann.

"Green Magnets" to save energy in accelerators

Margarita Synanidi — Thu, 27 Nov 2014 10:22:24 +0000

"Green Magnets" to save energy in accelerators
by Livia Lapadatescu (CERN), Thomas Hind (CERN)

Fig 1: Green Magnets developed at Danfysik
Image credit: Danfysik

A partnership of universities and industry have produced “Green Magnets” which give more than 95% electrical efficiency savings. The “Green Magnets” technology could be used to replace non-superconducting accelerator electromagnets.

The idea for the magnets, which work by using very strong permanent magnetic materials based on rare earth minerals and shaping them in such a way to provide the desired magnetic field, originated at the International Climate Summit in Copenhagen in 2009. The partners expressed a desire to save energy and cut carbon emissions in accelerators and identified magnets as their primary power consumer. Breaking their set target of reducing power consumption by 75%, they managed to achieve a 95% cut in energy use in the magnets, as well as removing the need for water cooling infrastructure, heavy cabling and large power supplies.

The magnets were developed through a project run by five partners from academia and industry (Aarhus University, Aalborg University, Aarhus School of Engineering, Sintex A/S and Danfysik A/S). With financial support coming from Danish Advanced Technology Foundation the consortium is able to replace non-superconducting electromagnets of up to 1 Tesla which need not more than +/- 25% field variation during operation.

Having overcome various technical challenges, such as temperature stability and radiation resistance, what remains now is the challenge of increasing the focus of labs on energy consumption and sustainability, in addition to successfully marketing the need for more energy efficient magnets such as the Green Magnets.

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permanent magnets

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Knowledge Technology Transfer

issue 11

First Energy Efficient RF Sources Workshop

Margarita Synanidi — Tue, 25 Nov 2014 13:29:01 +0000

First Energy Efficient RF Sources Workshop
by Erk Jensen (CERN), Charlotte Houghton (STFC)

Attendees of the EnEfficient RF Workshop at the Cockcroft Institute, June 2014.
Image credit: Cockcroft Institute

The first Energy Efficient RF Sources workshop, supported by EuCARD-2, took place in June 2014 at the Cockcroft institute in the UK. Over 40 delegates and 18 speakers were part of the two day workshop which discussed state-of-the-art RF sources.

In the early days of particle accelerators, RF experts concentrated their design work on cavities and amplifiers with large acceleration in mind. Later, when the beam currents in accelerators increased, the focus of their ingenuity shifted towards coping with beam loading, better beam stability and increasing beam power. With demands for ever increasing beam energy and power, the overall energy consumption has now clearly become a major concern; large future particle accelerators must remain economically and ecologically sustainable and acceptable, so the overall power conversion efficiency has taken centre stage. Optimization of this efficiency could reduce both power consumption and wasted energy, both relevant for the society at large. At this Daresbury workshop, these concerns were discussed among international experts, and many novel and interesting solutions to make better RF systems were proposed.

Workshop highlights included, pioneering ideas proposed to substantially increase the power conversion efficiency of high power klystrons. Klystrons are Multi-Megawatt RF power amplifiers at the heart of many particle accelerators. While present-day klystrons are limited to efficiencies below 70%, the proposed improvements may push efficiencies to 90%. Much attention was also devoted to high power solid-state amplifiers. These amplifiers are still limited to much smaller power limits than vacuum electronic devices, but the trend over the last decade is very promising; and it is predicted they will become important in the future. Inductive output tubes (IOT’s), combine the advantages of grid tubes, this allows them to run without DC current, i.e. at lower power consumption. With the advantages of high frequency klystrons, IOT’s do not yet reach the power levels needed in accelerators, but promise better efficiency. This has encouraged recent results and plans for further research.

The two-day workshop, which is part of the EnEfficient EuCARD-2 work package, addressed the above interesting and promising topics and more. The workshop included a tour of the Versatile Electron Linear Accelerator (VELA), located at the Daresbury Laboratory.

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Towards energy efficient particle accelerators

Margarita Synanidi — Mon, 24 Nov 2014 14:06:14 +0000

Towards energy efficient particle accelerators
by Mike Seidel (PSI) with Mathilde Chaudron (CERN)

Inductive Output Tube (IOT). Image credit: CPI.

The 2nd Workshop on Energy for Sustainable Science at Research Infrastructures was held the 23-25 October 2013 at CERN to discuss the challenges and potential solutions in energy efficiency. The workshop featured a talk from the EnEfficient network, the EuCARD-2 Work Package 3, which presented its plan to stimulate innovation in the energy efficiency of particle accelerators in the coming years.

Scarcity of resources, along with rising energy costs and climate change are ever growing concerns for the next generation of large accelerator based facilities. Indeed, the much increased performance of proposed new facilities comes together with anticipated increased power consumption. The network EnEfficient builds on this recent consciousness that accelerators have to be sustainable over the long term and socially acceptable by reducing their environmental impact and their energy consumption. It aims to federate the initiatives of research institutions and universities towards an efficient utilization of electrical power in 5 different areas: heat recovery, efficiency of Radio Frequency (RF) power generation, virtual power plant (improved adaptation to varying supply situation on grid), energy storage systems and low power beam transport channels.

As one of the networking activities a workshop on efficient RF generation will be organized in the spring of 2014. The picture shows the concept design of a multi-beam Inductive Output Tube (IOT). IOTs typically reach higher efficiency than traditional klystrons particularly where klystrons need to be operated below saturation. The utilization of this technology for the accelerator of the European Spallation Source (ESS) is presently being investigated which would result in electrical power savings of 3 MW. European

Additional participants are sought and are welcome in all themes of the EnEfficient network.

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