SAVVIE: Staying alive in variable, intermittent, low-power environments

Lead Research Organisation: University of Bristol
Department Name: Electrical and Electronic Engineering


Today's low-power electronic systems are designed to handle a high variability in the power demand, for example during transmissions from miniature wireless sensors. However these systems cannot cope with a highly variable power supply. If they are powered by an ambient energy harvester in an environment where the available power is low and sporadic, the system dies once the energy storage becomes depleted or damaged, with start-up being impossible if the power is not increased to a higher steady level. With an increasing number of potential applications of microelectronic systems calling for remote, embedded and miniaturized solutions, sporadic and low power supply and unpredictable energy storage needs to be addressed.

This project researches how to design robust and reliable electronics for situations where there is a variable, unreliable source of energy. A number of situations, or states, have been defined, according to the level of depletion of on-board energy storage, and to how variable the power supply is. In the most challenging states, for example where the input power is sporadic and spread over a wide range from nW to mW, modern electronics fails. We call this the "survival zone" and are investigating a combination of techniques from the areas of power electronics and asynchronous microelectronics design to allow devices to operate in this zone. Techniques include control circuits that are able to ride through variable voltages, the detection of states, and reconfigurable hardware resources and control algorithms to suit sporadic and sub-microwatt input power. The chief aim of this project is to produce survival zone design methods for the microelectronics design community.

Planned Impact

The scientific aims of the project support the development of unobtrusive healthcare and security devices and power saving techniques for electronic systems. Applications could be the enabling technologies for blanket monitoring of water supplies or wearable sensors for those with chronic illness. The transfer of results and skills to these areas will be carried out via joint projects, for example a large KTA project "Crossing the Clinical Boundary", placed at Durham/Newcastle, with direct links with practising heart surgeons and electro physiologists.

This project brings together two areas of engineering, power electronics and microelectronic design, which are traditionally separate, providing the opportunity to learn and to create systems that do more computation with less power, and in particular sporadic power that is difficult to harness. This will create a common language for much needed systems engineers who work at the boundary of electrical power engineering and computing. Project staff will spend time at leading European research organisations, such as IMEC, providing the project team with manufacturing and additional research experience. The project will allow the project teams to train up PhD students in most recent techniques, and it will underpin University teaching of the increasingly important areas of energy-aware microelectronic design, and ultra-efficient power electronic control for miniature energy harvesting to domestic-scale renewable energy generation.

The developed techniques will enhance efficiency, operability and survivability of microelectronics in sporadic power situations which are currently inaccessible to modern electronics. The developed methods will be presented to the wider community in an international workshop in Month 33 of the project. Throughout the project, courses and tutorials will be delivered at conferences, as is current practice by team members already (for example at DATE 2010, DDECS 2010, ASYNC 2010). The first such dissemination tutorials for this project are at PATMOS'12 and UK Electronics Forum 2012, both hosted by Newcastle, and ESWEEK 2013.

The project is supported by Texas Instruments (TI), a top multi-national hi-tech company and leader in semiconductor and power electronics markets. This collaboration will ensure that the work is targeted and relevant to the industry without compromising on the aspiration to create transformational enabling technologies for future devices. It will allow the results of the project to make direct impact on the energy-aware embedded system design methodology and electronics for energy harvesting sources and applications. The project plan includes an early physical demonstrator system, which will be used to prioritise challenges, with involvement from TI engineers. TI have supported previous projects at Bristol and introduced teams to their industrial research and manufacturing partners at key stages in research projects. Once concrete design tools have been established, UK companies will be used to commercialise results, for example Newcastle's recent spin out company i GXL, and also the UK companies and UK branches of international companies who are represented on Newcastle's and Bristol's Engineering advisory boards (e.g. Aptina, ARM, Cadence, Imagination, Sony, STMicroelectronics, TI, and Toshiba TREL).


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Description The Achilles heel of the Internet of Things is the power supply, and in particular the fact that even when the device is asleep it drains the battery. These devices need to be smaller and more wearable. Providing energy to power such small wearable devices is a significant challenge; as the device shrinks in size the capacity for energy storage is reduced too. One solution is for 'energy harvesting' devices, were the energy required is acquired passively from the surroundings, for example from energy generating fabrics. An alternative is active charging through electromagnetic fields (wireless power transfer).
These energy sources, when worn and therefore moved around by the user, become sporadic, unpredictable and variable. E.g. the wirelessly received power depends on the orientation of the device, the distance from the transmitter and clutter in a room. There are therefore moments when even sleep modes cannot be powered and the device fails and is unrecoverable.
We have developed
- the first reconfigurable circuits that adapt to the available power, and that do not fail when the power declines.
- a device that eliminates the need for battery and sleep modes, and permits the use of intermittent sources such as energy harvesting and wireless power transfer.
A key novelty is our circuits' ability to function at power levels that are orders of magnitude lower than the best commercially available sensing circuits, powering themselves from the signal they are is measuring without noticeably changing this signal! A first application is the front-end of wirelessly-powered worn medical sensors and Internet of Things devices, allowing these to wake-up only when there is power, thus reducing their size to a slither, by completely eliminating their bulky energy storage. We have proven this by implementing the detector as an integrated circuit (IC).
Exploitation Route This work is being extended to permit the harvesting from harvesting textiles that output sporadic spikes of power when bent or compressed. This again is applying the concept of reconfigurable electronics that adapts its circuit to the available power, with millisecond response times and energy budgets of pico Joules per transition.
We are also developing on-body medical sensors powered by wireless routers, textile inductive power coils, and energy harvesting materials.
Sectors Aerospace, Defence and Marine,Agriculture, Food and Drink,Digital/Communication/Information Technologies (including Software),Education,Electronics,Energy,Environment,Healthcare,Transport

Description In this project we showed that at electronic systems can be powered from miniature energy sources, previously thought to be too low-power and too variable to reliably power electronics. Following this work, we were contacted by other research groups who develop energy harvesters or wireless powering systems to help make their devices useful. These results where then used in the 2014-2019 SPHERE health sensing project, where one work package (2014-2016) took this forward to develop and Sensor Driven electronics that can monitor sensors using nanowatts of power. This meant energy harvesting was now viable and that batteries can last for decades in certain applications. The technology was prepared for commercial sampling using an EPSRC Acceleration Award. Once successfully trialed by industry, this technology was licensed in 2017 to Sensor Driven Ltd, which then received private investment and two Innovate UK awards. Sensor Driven currently employs engineers to create electronic sensors that do not require battery replacement. A study has been carried out for Sellafield to help with long-term waste storage, and long-life sensors are being developed for trails with various companies.
First Year Of Impact 2018
Sector Aerospace, Defence and Marine,Agriculture, Food and Drink,Digital/Communication/Information Technologies (including Software),Education,Electronics,Energy,Environment,Healthcare,Security and Diplomacy,Transport
Impact Types Societal,Economic

Description Impact Acceleration Commercialisation Award
Amount £63,048 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 04/2016 
End 03/2017
Description Functional materials Southampton 
Organisation University of Southampton
Country United Kingdom 
Sector Academic/University 
PI Contribution We have provided Southampton with energy harvesting circuits designed specifically for their functional materials, and designs for wireless power transfer devices.
Collaborator Contribution Southampton have provided us with functional materials, such as ferroelectret energy harvesters, and have made power transfer coils and antennas to our design.
Impact Multidisciplinarity: material science, analogue integrated design, low power electronic circuit design. Outcomes: New joint research, and working energy harvesting systems.
Start Year 2010
Description Newcastle low power electronics 
Organisation Newcastle University
Country United Kingdom 
Sector Academic/University 
PI Contribution We have provided new paradigms for energy management in energy harvesting systems, where power is intermittent.
Collaborator Contribution Newcastle have provided new paradigms for energy management in low power computing.
Impact We obtained a joint EPSRC grant through the outcomes of this collaboration, and this lead on to be invited into the £12M SPHERE project.
Start Year 2010
Title Wireless development platform 
Description Power quilt that has been configured as an educational kit for game developers and developers of wirelessly powered medical sensors. 
Type Of Technology Physical Model/Kit 
Year Produced 2016 
Impact This is yet to be transferred to interested parties and shown to the public. 
Company Name Sensor Driven Ltd 
Description SensorDriven enables monitoring devices to listen whilst being fully powered down, ensuring power resources are conserved for acting on relevant events. Our passive detector technology reacts to a wide range of physical parameters and presents a paradigm shift in power and data budgeting, delivering compact, ultra-long lifetime sensor solutions. 
Year Established 2017 
Impact 2 full-time engineers