首页 >> 推荐阅读 >> 正文

译:Connecting the green dots

来源: 时间:2011-7-15 10:04:00 点击:

In renewable-energy circles, there is a real excitement about Germany’s latest plans to move away from nuclear and towards renewable energy. The state of California has similarly raised its renewable-energy goals for electricity to 33% by 2020, while China has repeatedly outstripped its wind-energy targets and is on track to install 90 gigawatts by 2015.

However, large-scale renewable power, particularly electricity generated from the sun and wind, relies heavily on the electricity grid. The electricity grid is the way power is moved from generators to customers. While coal can be shipped to a city and burned in a nearby power station, renewable energy has to be generated wherever there is a lot of sun or wind. In China and the United States in particular, this can be a long way from the large cities. As a result, renewable energy often has to travel a long distance on the grid to reach consumers.

The grid is frequently weak in the rural areas that have good renewable energy resources, so absorbing all the available power can be difficult or even impossible. Across the United States, rural areas experiencing a boom in wind farms face an overloaded grid that doesn’t reach large cities on either coast. The 2010 China Wind Power Outlook, jointly released by the Global Wind Energy Council, the Chinese Renewable Energy Industries Association and Greenpeace China tells of similar challenges facing the rapid expansion of the wind power bases in China.

Power generated from the sun and wind is also intermittent: there is no power when the sun doesn’t shine and the wind doesn’t blow. There are a few ways that grid operators – the technicians responsible for keeping electricity moving through the grid – cope with intermittent power. They can draw renewable energy from a wide area, in the hope that the wind is blowing or the sun is shining somewhere. They can manage the customer demand by arranging to disconnect large users for a few hours. Finally, they can arrange for backup power generation by a controllable power source like hydropower or natural gas turbines. Grid operators can use a blend of all three of these strategies – but the first option particularly requires lots of strong, tightly integrated grid capacity between regions.

China is currently investing heavily to create this sort of tightly integrated, strong grid that can move renewable energy from the west and north to the large cities on the coast. However, building lots of new power lines is only the beginning of what is necessary to really scale up the proportion of renewable energy used by a country. There are many supporting policies, procedures and technologies needed to allow the grid operator to make the most of intermittent renewable power.

For example, it is important to have very precise weather forecasts, particularly 24 hours ahead. High-quality weather forecasts allow the grid operator to plan on receiving at least a minimum amount of renewable power to meet the expected customer needs. Then the operator does not need to schedule as much coal or other power to be generated, reducing pollution and saving fuel.

Renewable power can be more expensive to produce than options like coal and natural gas. This is partly because fossil fuels are often subsidised, directly or indirectly, and partly because renewable-energy technologies are not yet as mature as fossil-fuel technologies. The grid operator’s standard procedure is to use the cheapest power first. So the government must mandate that the grid operator purchase the renewable power even when it is not the cheapest option. This can be done in a variety of ways, including through a renewable-portfolio standard or something called a priority-dispatch requirement, but the goal of all of the tools is to change how the grid operator chooses which generators to use each hour.

One of the grid operator’s key responsibilities is to keep the grid stable by perfectly balancing the electricity generated with the electricity demanded at all times. A stable grid requires several supporting services, called “ancillary services” in the industry. These include services like backup generation that can come online within seconds or minutes in case a power station fails unexpectedly.

Backup generation is, of course, also one strategy to manage intermittent renewable power. However, in regions – like many in China – that are heavily dependant on coal for power, there may not be good backup generation options that can come online very quickly. For coal to act as backup generation, the power plant must be constantly burning fuel to keep the boiler hot, while it waits to be needed. Thus, backing up renewable energy with coal means there is little to no pollution benefit from using the renewable energy: the coal plant is running anyway. To really see the benefits of renewable energy, it is important for the grid operator to also have cleaner options for the “ancillary services”.

In Germany, the latest wind turbines include technology that allows them to provide some other ancillary services, such as reactive power. This is a great step towards integrating renewable power in the grid, but it does not necessarily solve the specific challenge of backup generation. To take full advantage of renewable power, the grid operator and decision makers need carefully to consider the full technical and procedural options for ancillary services.

A special report on the potential of renewable energy by the Intergovernmental Panel on Climate Change, published in May, confirmed that there is enough wind, water, sun and biomass to meet our energy needs with today’s technology. However, there are many barriers to utilising that resource effectively. Building and strengthening the grid is one piece of the puzzle, but just as important are the policies, procedures and technologies used to manage the grid today. These need to adapt and grow to seamlessly integrate renewable power. Grid operators in particular will be key to maximising the greenhouse-gas reductions that we might see from using renewable energy for electricity. They have a critical role to play in the work to safeguard the climate.

(译文如有出入请联系本会,来源于chinadialogue)

译   文:

让电网和绿色连接起来

 

  德国刚刚提出的摒弃核能、发展可再生能源的最新计划,着实给可再生能源业打了一针兴奋剂。加州已经作出了类似的决定,计划到2020年将其可再生能源的比重提升到33%。中国则一再重申其宏伟的风能目标,并正朝着2015年装机容量9000万千瓦的目标迈进。

  但是,大规模的可再生电力,特别是太阳能和风力发电,都严重依赖电网。电网就是把电力从发电者输送给消费者的通道。煤炭可以被运输到一个城市然后在其附近的电厂燃烧发电,但可再生电力只能在那些太阳能和风能丰富的地方生产,然后再通过电网输送。特别是在中美两国,这些可再生能源产地通常都离大城市非常遥远。因此,可再生能源也通常要在电网上“长途跋涉”才能到达消费者那里。
 
  但是,可再生能源丰富的农村地区的电网通常都很脆弱,因此要它吸收全部可利用的可再生电力非常困难,或者说根本就不可能。美国各地的农村的风电热潮面对着电网超载的压力,使电力无法输送到东西海岸的大城市。全球风能理事会、中国资源综合利用协会可再生能源专业委员会和绿色和平组织(中国)联和发布的《中国风电发展报告2010》指出,中国快速扩张的风电事业面临着同样的挑战。
 
  太阳能和风能发电的另外一个巨大问题是其间歇性:阳光并不是总有,风不是总在吹。对此,电网的运营商——负责电力在电网上输送的技术人员用来应对间歇性问题的办法屈指可数。首先是在一个较大范围内收集可再生能源,这样总会有有风的地方吧。其次是对用户需求进行统筹,在较多用户不用电的时候可以将其切断几个小时。再次是用水力发电和天然气发电等可控的手段作为备用方式。电网运营商经常把上述三种方法综合起来,但第一种方法尤其需要有一个联系紧密的强大电网把各地区整合在一起。
 
  中国目前正在大力投资建设这样一个联系紧密的强大电网,以便把可再生电力从西部和北部输送到沿海大城市。但是,一个国家要真正大规模提高可再生能源的比重,电网建设只是一个开端。要让电网运营商把间歇性的可再生电力充分利用起来,还需要有大量的支持性政策、程序和技术。
 
  比如,精确的天气预报至关重要,特别是24小时之内的。高质量的天气预报能够让电网运营商规划出满足客户预期需求的可再生能源最小额度,这样就不需要过多的燃煤或者其他电力来作为备用,从而减少污染并节省燃料。
 
  可再生能源的发电成本通常要比煤炭和天然气更高一些,部分原因在于化石燃料经常会得到直接或间接的补贴,还有部分原因在于可再生能源技术还不像化石燃料技术那样成熟。电网运营商的“标准流程”是先用最便宜的电力。这样一来,政府就必须强制电网运营商们购买可再生能源电力,尽管它们可能并不是最便宜的。要做到这一点,可以通过多种途径,包括可再生能源投资组合标准或者所谓的优先调度要求,但这些都会改变电网运营商对发电者的选择方式。
 
  电网运营商的一个关键责任就是通过发电和用电的全天候良好平衡,保持电网的稳定。一个稳定的电网需要多个支持性服务,即业界所说的“辅助服务”,包括备用发电等。备用发电必须要在电厂突发故障时在几分钟甚至几秒钟之内进行补位。备用发电当然也是应对间歇性可再生能源的方法之一。但是,很多对煤电高度依赖的(比如中国内的)地区,可能没有能够很快并网的备用发电方式。因为要把煤电作为备用发电方式,电厂必须不断烧煤才能保持锅炉的热度,以备不时之需。这样一来,用煤电作为可再生能源的备用发电方式就意味着可再生能源的环境效益被抵消殆尽,因为燃煤电厂还是在运行的。为了真正实现可再生能源的效益,电网运营商必须找到更清洁的 “辅助服务”方式。
 
  德国最近建成的风力电场采用的技术可以让他们采取其他辅助服务的方式,如无功电力。这是把可再生能源融入电网的重要一步,但它仍然无法完全解决备用发电的具体问题。为了充分利用可再生能源,电网运营商和决策者必须对辅助服务的所有技术和程序方式进行深入透彻的考虑。
 
  IPCC五月份发布了一份关于可再生能源潜力的特别报告,断言说在今天的技术条件下,风能、水能、太阳能和生物质能完全可以满足全世界的能源需求。但是,要充分利用这些能源还面临着众多障碍。电网的建设和强化只是其中一个方面,电网经营的政策、程序和技术也同样重要。这些都要通过适应和发展,实现与可再生能源的无缝对接。要通过可再生能源发电实现温室气体排放的最小化,电网运营商的作用尤其关键。他们在保护气候的工作中扮演者至关重要的角色。
浙江正泰公益基金会 浙ICP备11034570号 2000-2011 THE COMMONWEAL FOUNDATION OF CHINA
浙江省杭州市下城区中山北路598号西子花园柳莺苑11B 热线电话:0571—89710110 89710106 邮编310014 电子邮箱:dtxd@ztgy.org