integrating energy storage in off-grid telecoms systems - ITM Power

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HYDROGEN: INTEGRATING ENERGY STORAGE IN OFF-GRID TELECOMS SYSTEMS CASE STUDY 02

Case Study 02 Hydrogen: Integrating Energy Storage in Off-Grid Telecoms Systems

Background ITM Power is a developer of hydrogen energy systems based on electrolysis. There are numerous applications for such systems in energy storage, clean fuel production and vehicle refuelling. This case study describes a scoping study to design and specify a hydrogen system for use by telecommunication companies for powering remote off-grid transceiver stations. The objectives were to ensure reliable telecoms availability, extend component life and fully exploit on-site renewable power sources (solar PV and wind power). Telecom base transceiver stations are often positioned in remote locations where grid connection or regular replacement of conventional fuel is unrealistically expensive. Current offgrid renewable power systems employ wind and/or solar, require backup during gaps in supply and use batteries to store electricity. A study undertaken by ITM Power on behalf of a major telecommunications system operator showed that on-site hydrogen generation and storage can protect batteries from deep discharge by absorbing seasonal swings in supply and providing power (via a fuel cell) during periods of low availability. When compared with PV-battery systems, the identified approach improves capture of renewable energy at times of high availability, reduces the capacity requirements of the wind, PV and battery components, and extends battery life.

“Hydrogen is ideal for long-term bulk energy storage on a seasonal timescale, while batteries are best suited for short-term energy storage.” Seasonal Energy Storage System Based on Hydrogen for Self Sufficient Living M. Bielmann, U.F. Vogt, M. Zimmermann, A. Züttel, J. Power Sources, 196 (2011) 4054


Scoping Study The study site, an existing off-grid telecommunications transceiver station in the British Isles, presently employs wind and solar power with lead-acid battery storage. An annual minimum in stored energy occurs as a function of the availability of renewable power and for several weeks the battery system is highly stressed with the state of charge dropping easily to 30% or less. This has a consequent negative impact in terms of battery life and may require supplementary power immediately (e.g. from the grid if available or an on-site diesel generator). In contrast to batteries, hydrogen storage can experience very deep discharge without shortening system life. Hybrid storage systems can exploit the benefits of both technologies, using batteries for daily cycling and hydrogen to negotiate seasonal variations. The susceptibility of batteries to self-discharge also makes hydrogen a more suitable seasonal storage medium.

Current hydrogen systems typically use delivered bottles to power a fuel cell, but ITM can eliminate the need for bottle deliveries through the use of a water electrolyser connected directly to the renewable power source. HBox Solar is a 14 bar passive electrolyser with a minimum system efficiency of 78%, 1.3kWp rating and an output of up to 3 slpm H2 . A hybrid system incorporating this high efficiency electrolyser and fuel cell in addition to the wind, solar and battery storage was modelled to optimise the operation of the telecoms system so that it could negotiate periods of constrained renewables supply, yet maintain the state of charge of the batteries well above the minimum specified by the supplier for a long working life.

100

5

90 4

70 60

3

50 40

2

30 20

1

10 0

0 Jan

No Hydrogen

Feb

Mar

Apr

Battery

May

Jun

Tank level

Jul

Aug

Sep

Oct

Nov

Dec

Hydrogen Tank Level (kg)

Battery State of charge (%)

80


Building on the technology developments ITM has identified the following role for on-site hydrogen generation in hybrid off-grid energy storage: • Electrolyser to absorb seasonal swings in supply and accept low/variable input levels directly, removing the need to store renewable energy in the battery first (hence reducing conversion losses) • FC operation to prevent battery deep-discharge

• Reduce wastage of renewable energy that otherwise could not be used/stored • Reduce the size of wind/solar generators needed to meet the load year-round • Improve mast availability and reduce the need for backup generation/emergency callouts

• Store energy long-term by exploiting hydrogen’s ability to avoid self-discharge • Separate power/energy components, allowing component sizing to be optimised for individual applications so reducing costs ITM is currently investigating telecoms markets where on-site hydrogen generation and storage can play a key role, including finding the optimal balance between wind/PV supply and hydrogen/battery capacity for a range of geographical locations. ITM is able to carry out similar scoping studies for interested operators and build turnkey plant.

INPUT

SUBSYSTEMS

OUTPUT

TELECOMS

1. PRIMARY LOADS

FC

PERIPHERAL

WIND CAPACITY 2. PRIMARY POWER

LOCAL RESOURCE

CAPACITY FACTOR

PV RATING

3a. SEASONAL STORAGE

ECONOMIC

ELECTROLYSER RATING

3b. DAILY STORAGE

Hybrid Hydrogen System Design Logic

TANK SIZE

BATTERY CAPACITY

ITM Power PLC 22 Atlas Way Sheffield S4 7QQ T: +44 (0) 114 244 5111 W: www.itm-power.com 6588