Serial Hybrid Kinetic Energy Storage Systems - SHyKESS

这项提议是关于一种非常特殊的能源储存，以支持电网。随着我们对发电进行脱碳，目前储存能源的理由非常充分。世界已经到了一个非常有趣的地步，最便宜的电力实际上来自风能和阳光，但不幸的是，这些发电形式只有在主要资源可用时才能发电--即风力涡轮机只有在刮风时才能发电，而(大多数)太阳能只能在阳光灿烂的时候发电。只要这些可再生能源只占我们所有发电量的一小部分，风能和太阳能的间歇性就完全不成问题--因为我们可以控制燃煤和燃气发电厂的发电量。然而，如果我们要从可再生能源中产生高比例的电力，我们将需要能够储存大量的能源。现在，有许多不同的方式来储存能量。没有一种形式可以解决我们所有的需求。能量存储必须发展成适用于大范围的时间尺度和大范围的大小。每个正在开发的系统都有自己独特的一套优缺点。成本在所有情况下都是极其重要的：能源储存极其昂贵。大多数人没有意识到，即使是目前最好的商业产品，能源储备的成本与其所包含的能源价值之间的比例通常是1000：1。生命周期也极其重要。如果给定储能器的寿命只有5000个循环，则必须在5000个循环后更换该储能器，并且在此基础上，它将添加到已通过它的能量的成本通常为~20%。周转效率也很重要，如果你损失了进入商店的所有能源的20%，这将进一步增加高达20%的成本(但通常更接近10%，因为输入的能量通常比输出的能量价值低得多)。这项建议旨在研究一个似乎在几毫秒到几十个小时的时间范围内提供能量存储的系统。该系统包括两个不同的能量存储，它们以“串联”的方式连接在一起，也就是说，电网只有一个输出端。其中一个能量储存装置是一个非常大的飞轮。第二种是典型的压缩空气蓄能，但也可以是高水头抽水蓄能、抽水蓄热或基于液化空气的储能。与电网的连接是通过一个大型同步发电机实现的。这些系统只适用于中到大型-功率在50兆瓦以上，储能容量在250兆瓦时及以上的系统。它们不适合城市地区。对于那些(许多)适合它们的情况，这些系统似乎提供了以非常有竞争力的成本提供极高性能的潜力。最重要也是最独特的是，同步电机的飞轮和转子的组合赋予了这些存储器大量的“真正的惯性”。惯性听起来像是一件坏事，但在电力系统的背景下，它是一件非常好的事情，它存在于蒸汽轮机驱动的发电的所有旋转转子中。随着我们不再使用煤炭、石油和天然气发电，我们正在关闭这些大型旋转发电机，我们正在失去以前作为免费服务存在的惯性。惯性越小，系统对负荷或发电量变化的反应就越快。如果我们让太多的惯性从我们的电力系统中消失，我们就会变得非常容易受到系统失控关闭的影响，原因要么是意外的天气波动、通信网络故障，要么是恶作剧的网络攻击，这些攻击可以利用系统的敏感度，从相对较小的行动引发不成比例的大事件。

This proposal is about energy storage of a very specific kind to support the electricity grid. The case for energy storage is extremely strong at the moment as we decarbonise electricity generation. The world has reached the very interesting point where the cheapest electricity actually comes from wind and sunshine but these generation forms unfortunately produce electricity only when the primary resource is available - i.e. wind turbines make electricity only when the wind blows and (most) solar power can only make electricity when the sun is shining. So long as these renewables comprise only a small proportion of all of our generation, the intermittency of wind and solar power is no problem at all - because we can control the generation being obtained from coal-fired and gas-fired power stations. However, if we are to generate high fractions of all of our electricity from renewables, we will need to be able to store large amounts of energy. Now, there are many different ways to store energy. No one form is a solution for all of our needs. Energy storage has to developed to be suitable over a large range of timescales and a large range of sizes. Each system being developed has its own particular set of advantages and disadvantages. Cost is extremely important in all cases: energy storage is extremely expensive. Most people do not realise that even with the best commercial offerings at present, the ratio between the cost of an energy store and the value of the energy that it contains is typically 1000:1. Lifetime is also extremely important. If a given energy store has a lifetime that is only, say, 5000 cycles, then that energy store must be replaced after 5000 cycles and the cost that it will add to the energy that has passed through it will typically be ~20% on this basis. Turnaround efficiency is also important, if you lose 20% of all of the energy that comes into the store, this adds a further cost that could be anything up to 20% (but would usually be more like 10% because the input energy is usually much less valuable than the output).This proposal sets out to examine a system that appears to offer energy storage over a range of timescales between milli-seconds and tens of hours. The system comprises two distinct energy stores connected in a "serial" fashion in the sense that there is only one output to the grid. One of these energy stores is a very large flywheel. The second is typically a compressed air store but it may also be a high-head pumped hydro store or a pumped-thermal store or an energy store based on liquefied air. The connection to the grid is via a large synchronous generator. These systems are suitable only at medium-to-large scale - powers above 50MW and energy storage capacities in the order of 250MWh and above. They are not suited for urban locations. For those (many) situations where they are suited, these systems appear to offer the potential for extremely high performance at very competitive costs. Most importantly and also most distinctively, the combination of the flywheel and the rotor of a synchronous machine endows these stores with substantial amounts of "real inertia". Inertia sounds like a bad thing but in the context of electrical power systems it is an extremely good thing and it is present in all of the spinning rotors in steam-turbine-driven power generation. As we move away from generation using coal, oil and gas, we are switching off these big rotating generators and we are losing inertia that was previously present as a free service. With lower inertia, the system responds more suddenly to changes in load or generation. If we allow too much inertia to disappear from our electricity system, we become very vulnerable to uncontrolled system shutdowns from either unexpected weather fluctuations, glitches in communications networks or from mischievous cyber-attacks which can use the system sensitivity to trigger disproportionately large events from relatively small actions.