GasNetNew - The role of the gas network in a future decarbonised UK

通过燃烧天然气来加热室内空间约占英国总二氧化碳排放量的30%。大约有2300万户家庭连接到天然气网络。每燃烧1公斤的气体可产生约12千瓦时的热量，并释放约4公斤的二氧化碳。在未来的净零排放的英国，这种情况不可能持续下去，而且使用任何已知的技术在单个建筑中捕获二氧化碳是完全不可能的。许多人认为氢应该取代天然气在天然气网络中。从技术上讲，这是可行的。氢可以通过电解或从天然气中产生。在后者的情况下，“碳捕获”方法可以收集大部分产生的二氧化碳并将其泵入地下。然而，在所有情况下，通过天然气网络分配氢气不一定是最明智的做法。该项目将回答如何在未来零净的英国最好地利用现有天然气网络的不同部分的问题。即使有碳捕获，从天然气中生产氢气也会产生一些二氧化碳排放。通常是>5%的转义。使用可再生电力通过电解制造“绿色”氢，然后在锅炉中燃烧，每使用10千瓦时的电力，向家庭提供的热量不到7千瓦时。相比之下，使用电动热泵每消耗10千瓦时的电力，就能提供40千瓦时的热量。尽管生产氢气用于供暖还有其他优点，但在英国的许多地区，这是否是最佳选择仍然值得怀疑。现有基础设施的很大一部分很可能将用于在全国范围内分配氢气。然而，网络的某些特定部分可以以不同的方式得到更好的利用。这个项目将探索天然气网络这些部分的不同可能用途。所有这些潜在的用途主要是为了解决如果热泵作为主要供暖机制在英国广泛部署会出现的问题。部分天然气网络未来的一个可能用途是向物业输送非饮用水。这些水可以作为低温热源来支持热泵。一种新型热泵将流入的水变成冰浆，并将冰浆丢弃，稍后再融化。这种“潜热泵”（LHP）可以从冷水中提取大量热量（12L的水提供约1kWh的热量）。这些热量在大约0摄氏度时从水中产生，因此，即使在外部空气非常冷的情况下，LHP的性能系数（COP）也可以达到40摄氏度。对于大多数空气源热泵来说，COP在非常寒冷的天气下急剧下降，而且由于显而易见的原因，COP在非常寒冷的天气下影响最大。天然气网络未来的第二个可能用途是作为回收（收集）网络，而不是作为输送（分配）网络。在这里，通过气体网络返回的流体将是一种化学物质的水溶液，这种化学物质在释放热量的特性下被水化（与水混合）。只有在非常寒冷的天气才会采取这种措施。氯化钙和硫酸镁是两种非常便宜的盐，溶解在水中会释放热量。还有其他一些廉价的物质在与水反应时释放出大量的热量。最后，如果水是在天然气网络的低压层输送的，那么天然气网络的高压层就可以自由地用于其他用途。一个非常有吸引力的可能性是使用这些部件作为压缩空气储能系统的压力容器。该系统将同时能够协助电力传输系统，在南北电力流量大的时候从北向南进行平行传输。这些主张对关键的社会利益相关者（包括政策制定者、潜在企业和公共最终用户）的接受程度如何，将是它们在现实世界可行性的组成部分，因此也将在这里进行研究。

Heating indoor spaces by burning natural gas accounts for ~30% of the UK's total CO2 emissions. Around 23 million properties are connected to the gas network. Each 1kg of gas burned delivers ~12kWh of heat and releases ~4kg of CO2. That cannot continue in a future net-zero UK and capturing CO2 at individual buildings is completely implausible using any known technology.Many consider that hydrogen should replace natural gas in the gas network. Technically, this is feasible. Hydrogen can be produced from electrolysis or from natural gas. In case of the latter, 'carbon-capture' methods can collect most of the resulting CO2 and pump that underground. However, distributing hydrogen through the gas network might not necessarily be the most sensible course of action in all cases. This project will answer the question about how best to use different parts of existing gas network in a future net-zero UK. Even with carbon-capture, producing hydrogen from natural gas does cause some CO2 emissions. Typically >5% escapes. Using renewable electricity to make 'green' hydrogen via electrolysis and then burning that in boilers delivers less than 7kWh of heat into homes for every 10kWh of electricity used. By contrast, using electrically driven heat pumps can deliver 40kWh of heat for every 10kWh of electricity consumed. Although there are other advantages to producing hydrogen for heating, it remains questionable whether this is optimal in many parts of the UK.It is very likely that a large fraction of the existing infrastructure will be used for distributing hydrogen across the country. However, some specific parts of the network could be better exploited in a different way. This project will explore the different possible uses for those parts of the gas network. All of these potential uses are motivated mainly by solving problems that would arise if heat pumping were deployed very extensively in the UK as the primary heating mechanism. One possible future use for parts of the gas network is to feed non-potable water into properties. This water could serve as the source of low-temperature heat to support heat pumps. A new variety of heat pump turns incoming water into an ice slurry and discards the slurry to melt again later. This 'Latent Heat Pump' (LHP) can extract a lot of heat out of cold water (12L of water provides ~1kWh of heat). That heat emerges from the water at about 0C and as a consequence, the LHP can have a coefficient-of-performance (COP) >4 even when the outside air is very cold. For most air-source heat pumps, the COP falls sharply in very cold weather and, for obvious reasons, the COP matters most in very cold weather.A second possible future use for the gas network is to serve as a return (collection) network rather than as a delivery (distribution) network. Here, the fluid returning through the gas network would be an aqueous solution of a chemical that was hydrated (mixed with water) at the property to release heat. This measure would be taken only in very cold weather. Calcium Chloride and Magnesium Sulphate are two very cheap salts that release heat when dissolved in water. There are other inexpensive substances that release large quantities of heat upon reacting with water.Finally, if water was being conveyed in the low-pressure tiers of the gas network, the high-pressure tiers of the gas network would be free for another use. A very attractive possibility here would be to use those parts as the pressure vessel for a compressed air energy storage system. That system would simultaneously be able to assist the electricity transmission system by doing a parallel transmission from North to South at times of high North-South power traffic. How acceptable each of these propositions is to key social stakeholders (including policy makers, prospective business, and public end-users) will be integral to their real-world viability, and so will be examined here also.