The Use of Geothermal Energy for the Decarbonisation of Heat in Greater Manchester

地球的气候正在变暖，科学证据表明，这是由于二氧化碳等温室气体在煤，石油和天然气等化石燃料燃烧过程中排放。增加的温室气体越多，地球就会变得越热，因此减少温室气体的排放是我们都应该关心的事情。我们可以通过使用不涉及燃烧化石燃料的可再生能源来减少排放。使用风能或太阳能发电在英国已经取得了成功，尽管使用化石燃料供暖仍然很普遍，因为大多数房屋和办公室都有燃气或燃油锅炉来提供供暖和热水。一个可能的低碳替代方案是使用地热能的热量。这涉及到利用地球内部存在的自然热量。地热能是指从地表以下几米到几公里深处的任何热量。你进入地球越深，它就越热。在最初的10米，岩层被太阳加热，在此之下，更深层的岩石被来自地球核心的辐射加热。温度随深度增加的速率称为地热梯度。曼彻斯特以下的地热梯度约为每公里28摄氏度（degC）。例如，如果表面温度是10摄氏度，那么在曼彻斯特以下1公里处的温度将是38摄氏度（10+28）。为了吸收这些热量，你需要水。来自周围岩石的热量被传递到储存在这些岩石深处的水中。如果地质条件合适，可以将其抽到地表，用于建筑物、温室或游泳池的供暖。如果水可以从岩石中自然流出，它就被称为渗透性含水层。这种渗透性可能是由于岩石颗粒之间的相互连接的空间（称为孔隙度），你可以把它想象成一个洗澡海绵。并非所有的岩石颗粒之间都有这种空隙，它们的孔隙度很低或没有。然而，如果这些岩石破裂或断裂，水仍然可以流过它们。想象一下撞到放在地上的一块玻璃。水仍然不会流过单个碎片，但可以通过裂缝找到它的路。同样，断裂的岩石仍然可以是可渗透的含水层。一组特殊的含水层出现在曼彻斯特以下的煤矿中。这些含水层不是天然的，但渗透性是由成千上万的男人、妇女和儿童在开采煤炭时经历巨大困难而挖掘的隧道造成的。如果我们能用他们的辛勤劳动来为我们的家园供暖，而不是用煤，而是用从这些地下空隙中提取的温水，这将是多么美妙的遗产。这个项目的主要目的是绘制这些地下蓄水层和矿井的地图，这样我们就能找到最好的地方来钻探和提取地热能。要做到这一点，我们需要“看”到地球使用的方法，如地震反射勘测。我们把声波发射到地球上，并测量它们返回的时间，有点像蝙蝠在觅食时所做的那样。这给了我们一幅不同地层及其在地球中位置的“图画”。然后，我们在三个维度上追踪这些，以显示它们在整个曼彻斯特的深度是如何变化的。如果我们知道深度，我们就可以用地热梯度来预测水温。在大曼彻斯特地区，人们钻了许多孔（称为威尔斯），以勘探煤、水和天然气等自然资源。它们让我们直接了解我们脚下的岩石类型，以及它们是否能够产生地热能热水。通过绘制这些含水层的深度和温度，我们可以设计威尔斯井来提取热量，并在我们的大曼彻斯特脱碳前进。

The earth's climate is warming, and scientific evidence shows that this is due to greenhouse gases like carbon dioxide being emitted during the combustion of fossil fuels such as coal, oil, and natural gas. The more greenhouse gases that are added, the hotter the earth will become, and so reducing their emissions is something we should all care about. We can reduce emissions by using renewable sources of energy which do not involve the burning of fossil fuels. Generation of electricity using wind or solar has been successful in the UK, although the use of fossil fuels for heat is still widespread as most houses and offices have a gas or oil boiler to provide heating and hot water. One possible low-carbon alternative is to use heat from geothermal energy. This involves harnessing the natural heat present within the earth. The term geothermal energy refers to any heat derived from the ground, from depths of a few metres to multiple kilometres beneath the Earth's surface.The deeper you travel into the earth the hotter it becomes. In the first 10 meters, layers are warmed by the sun, below this the deeper layers of rock are heated by radiation from the earth's core. The rate of temperature increase with depth is known as the geothermal gradient. Below Manchester the geothermal gradient is around 28 degrees Celsius (degC) per kilometre. For example, if the surface temperature is 10degC then at 1km below Manchester the temperature of will be 38degC (10+28). To extract this heat, you need water. Heat from the surrounding rock is transferred into water stored within these rocks at depth. If the geology is right this can then be then pumped to surface and used to warm buildings, greenhouses, or swimming pools. If water can flow naturally from the rock, it is described as a permeable aquifer. This permeability may be due to interconnected space (known as porosity) between the grains in the rock, you can think of it as being like a bath sponge. Not all rocks have this space between the grains, they have low or no porosity. Water may still be able to flow through these rocks, however, if they are broken or fractured. Think of hitting a pane of glass placed on the ground. Water would still not flow through the individual pieces but could find its way through the cracks. In the same way, fractured rocks can still be a permeable aquifer. A special group of aquifers occurs in the coal mines below Manchester. These aquifers are not natural, but the permeability is created by the tunnels dug out, by thousands of men, women and children undergoing great hardship to mine coal. What a fantastic legacy if we could then use all their hard work to heat our homes, not with coal, but with warm water extracted from these underground voids.The main aim of this project is to make maps of these underground aquifers and mines so we can find the best places to drill and extract this geothermal energy. To do this we need to "look" into the earth using methods such as seismic reflection surveying. We send sound waves into the earth and measure the time taken for them to come back, a little like a bat does when hunting for food. This gives us a "picture" of different layers and their position in the earth. We then trace these in three dimensions to show how their depth varies under the whole of Manchester. If we know the depth, we can predict the temperature of the water using the geothermal gradient. In Greater Manchester many holes (called wells) have been drilled to explore for natural resources such as coal, water and natural gas. They give us a direct view of what types of rocks are below our feet, and whether they are able to produce heated water for geothermal energy. By mapping the depth and temperature of these aquifers we can design wells to extract the heat and move forwards in our decarbonisation of Greater Manchester.