ELECTRICAL RESILIENCE
Are BESS systems a ‘green alternative’ to diesel?
Tomas Jucas, a principal electrical engineer within the National Healthcare Team at Mott MacDonald, presents what he dubs an ‘open review of the proposition that Battery Energy Storage Systems could be considered a green alternative to carbon-emitting standby diesel generators located at healthcare sites’.
The UK’s Department for Business, Energy & Industrial Strategy (BEIS) has developed an Electricity Supply Emergency Code (ESEC) which outlines the actions to be taken, and the timeframes, for electrical power stability recovery during an electrical power crisis. In the event of a substantial emergency, ESEC enables equal distribution of electricity supply to customers as far as reasonably practicable, while ensuring that pre-designated ‘protected sites’ maintain supplies for as long as possible.1
While the assumption
is that the majority of healthcare sites would be considered ‘protected’, official recognition from their respective Distribution Network Operators (DNO) would confirm this.
Power restoration The assumptions above are set out in more detail within the Northern Powergrid (NPG) document, Understanding emergency power cuts. Frequently Asked Questions, which states that healthcare sites classified as ‘protected sites’ are those which are ‘major hospital facilities with accident and emergency departments’.2 NPG, in its letter dated December 2022 sent to its priority customers, clarifies that no power restoration priority over other electrical power consumers is guaranteed to be provided by the service-provider, regardless of the healthcare site’s priority class. As regards power restoration to hospitals in general, the initial ‘FAQ document’ states that ‘Most hospitals have back-up generators to ensure that they can continue to operate in the event of power disruption’. A recommendation is made to review any potential risks to the site, and to have strategies in place should power cuts last longer than three hours. Additionally, unprotected sites will be subject to the effects of a variable rota disconnection plan (VRDP), where the loss of power time window is predetermined. Power loss during rota disconnection periods equates to losing the primary electrical supply for 3-4 hours.
Figure 1: The BEIS Electricity Supply Emergency Code was published in revised form in November 2019.
UK Power Networks (UKPN) has a user-friendly ‘tracker’ of annual power cut length and impact on the number of consumers, which provides insight into service reliability. The indicated average power cut length, as per the 2018/2019 period, was estimated to be 30 minutes. The level of resilience depends on the stability of the regional grid, which has to be acknowledged as an element of risk if and when innovative engineering proposals are put forward for consideration.
Resilience requirements within healthcare Preliminary recommendations and guidance relating to electrical distribution throughout NHS sites are provided within Health Technical Memorandum (HTM) 06-01. The resilience of electrical services, alongside services redundancy, are essential to ensure continuous hospital operation during a loss of primary electrical supply (PES). HTM 06-01 provides information on decision-making as regards electrical services resilience with respect to loss of mains (LoM) creating risks to patients and business continuity. Figure 2 presents both types of
risk gradings, from high to low: business continuity on the left, and patient risk on the right. The electrical resilience aspect should be considered from a final circuit resilience perspective, as well as from the whole site load perspective. When options are considered, it is paramount to abide by the requirements set out within EREC G99 and BS 7671 Chapter 82 to ensure safe operation, sustainability, and efficient use of energy.
Replacing standby diesel generators with Battery Energy Storage Systems The next section of this article relates to the whole site (or section of the site resilience), and the proposed replacement of existing standby diesel generator(s) with Battery Energy Storage Systems (BESS). It should be noted that the level of desired resilience from a site coverage perspective, to an even greater extent
Figure 2: An excerpt from HTM 06-01 indicating levels of clinical and business risk. September 2023 Health Estate Journal 53
Image courtesy of the Department of Health & Social Care
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120
