Producing enough energy to meet our needs has become a serious problem.

生产足够的能源来满足我们的需要已成为一个严重的问题。

Demand is rising rapidly, because of the world's increasing population and expanding industry.

由于世界人口的增长和工业的发展，需求正在迅速增长。

Burning fossil fuels, like gas, coal and oil, seriously damages the environment and they'll eventually run out.

燃烧化石燃料，如天然气、煤和石油，会严重破坏环境，并且它们最终都会耗尽。

For a number of years now, scientists have been working out how we can derive energy from renewable sources, such as the sun and wind, without causing pollution.

多年来，科学家们一直在研究如何在不造成污染的情况下从可再生资源中获取能源，比如太阳和风。

Today I'll outline marine renewable energy - also called ocean energy - which harnesses the movement of the oceans.

今天，我将概述海洋可再生能源，也被称为海洋能源，它利用海洋的运动产生能量。

Marine renewable energy can be divided into three main categories: wave energy, tidal energy and ocean thermal energy conversion, and I'll say a few words about each one.

海洋可再生能源可分为波能、潮汐能和海洋热能转换三个主要类别，我将分别进行一些说明。

First, wave energy.

首先，波能。

Numerous devices have been invented to harvest wave energy, with names such as Wave Dragon, the Penguin and Mighty Whale, and research is going on to try and come up with a really efficient method.

人们发明了许多设备来获取波能，这些设备的名字有“波浪龙”、“企鹅”和“巨鲸”等。人们也进行着研究，试图找到一种真正有效的方法。

This form of energy has plenty of potential, as the source is constant, and there's no danger of waves coming to a standstill.

这种形式的能量有很大的潜力，因为它的来源是恒定的，没有波浪静止的危险。

Electricity can be generated using onshore systems, using a reservoir, or offshore systems.

电力可以利用陆上系统、水库或近海系统产生。

But the problem with ocean waves is that they're erratic, with the wind making them travel in every direction.

但是海浪的问题是它们很不稳定，风让它们朝各个方向移动。

This adds to the difficulty of creating efficient technology: ideally all the waves would travel smoothly and regularly along the same straight line.

这给创造高效技术增加了难度：理想的情况是，所有的波浪都沿着同一条直线平稳而有规律地行进。

Another drawback is that sand and other sediment on the ocean floor might be stopped from flowing normally, which can lead to environmental problems.

另一个缺点是，海底的沙和其他沉积物可能无法正常流动，这可能导致环境问题。

The second category of marine energy that I'll mention is tidal energy.

我要提到的第二类海洋能源是潮汐能。

One major advantage of using the tide, rather than waves, as a source of energy is that it's predictable: we know the exact times of high and low tides for years to come.

利用潮汐而不是波浪作为能量来源的一个主要优点是，它是可预测的：我们可以预测未来几年潮汐涨落的确切时间。

For tidal energy to be effective, the difference between high and low tides needs to be at least five metres, and this occurs naturally in only about forty places on Earth.

为了使潮汐能有效，涨潮和落潮之间的高度差至少需要五米，而在自然条件下在地球上只有大约四十个地方符合条件。

But the right conditions can be created by constructing a tidal lagoon, an area of sea water separated from the sea.

但是通过建造潮汐泻湖--一个与海洋分离的海水区域，我们可以创造这样的条件。

One current plan is to create a tidal lagoon on the coast of Wales.

目前的一个计划是在威尔士海岸建造一个潮汐泻湖。

This will be an area of water within a bay at Swansea, sheltered by a U-shaped breakwater, or dam, built out from the coast.

这将是在斯旺西的海湾内的一个水域，它会受一个从海岸建造的U形防波堤，或大坝的庇护。

The breakwater will contain sixteen hydro turbines, and as the tide rises, water rushes through the breakwater, activating the turbines, which turn a generator to produce electricity.

防波堤将包含16个水轮机，当涨潮时，水冲过防波堤，激活了涡轮机，使发电机发电。

Then, for three hours as the tide goes out, the water is held back within the break water, increasing the difference in water level, until it's several metres higher within the lagoon than in the open sea.

然后，在退潮的三个小时里，海水被挡在防波堤里，增加了水位的差异，直到它在泻湖里比在公海里高出几米。

Then, in order to release the stored water, gates in the breakwater are opened.

然后，为了释放储存的水，防波堤的闸门被打开。

It pours powerfully out of the lagoon, driving the turbines in the breakwater in the opposite direction and again generating thousands of megawatts of electricity.

水有力地从泻湖中涌出，向反方向推动防波堤的涡轮机，并再次产生数千兆瓦的电力。

As there are two high tides a day, this lagoon scheme would generate electricity four times a day, every day, for a total of around 14 hours in every 24 - and enough electricity for over 150,000 homes.

由于每天有两次涨潮，这个泻湖计划将每天发电四次，每24小时中发电14小时，足够超过150,000个家庭使用。

This system has quite a lot in its favour: unlike solar and wind energy it doesn't depend on the weather; the turbines are operated without the need for fuel, so it doesn't create any greenhouse gas emissions; and very little maintenance is needed.

这个系统有很多优点：与太阳能和风能不同，它不依赖于天气；涡轮机的运行不需要燃料，所以它不会产生任何温室气体排放；而且几乎不需要维护。

It's estimated that electricity generated in this way will be relatively cheap, and that manufacturing the components would create more than 2,000 jobs, a big boost to the local economy.

据估计，以这种方式发电的成本相对较低，同时，制造这些部件将创造2000多个就业机会，大大促进当地经济的发展。

On the other hand, there are fears that lagoons might harm both fish and birds, for example by disturbing migration patterns, and causing a build-up of silt, affecting local ecosystems.

另一方面，人们担心泻湖可能危害鱼类和鸟类，例如扰乱迁徙模式，造成淤泥堆积，影响当地生态系统。

There are other forms of tidal energy, but I'll go on to the third category of marine energy: ocean thermal energy conversion.

还有其它形式的潮汐能，但我会继续讲第三类海洋能源：海洋热能转换。

This depends on there being a big difference in temperature between surface water and the water a couple of kilometres below the surface, and this occurs in tropical coastal areas.

这种能源依赖于海平面海水与在海面以下几公里海水的巨大温差，而这种情况发生在热带沿海地区。

The idea is to bring cold water up to the surface using a submerged pipe.

这种办法是利用水下管道将冷水带到表面。

The concept dates back to 1881, when…

这个概念可以追溯到1881年，那时……