Harvesting Solar Energy from Space從太空捕獲太陽能

馬泰奧·切里奧蒂/文　陳儉貞/譯

The idea of space-based solar power （SBSP）—using satellites to collect energy from the sun and “beam” it to collection points on Earth—has been around since at least the late 1960s. Despite its huge potential， the concept has not gained sufficient traction1 due to cost and technological hurdles.

太空太陽能是指利用衛星從太陽收集能量，并將其“傳送”到地球上的收集點。這一概念至少在20世紀60年代末就出現了。然而，盡管潛力巨大，由于成本和技術難題，太空太陽能尚未獲得足夠的關注。

Can some of these problems now be solved？ If so， SBSP could become a vital part of the worlds transition away from fossil fuels to green energy.

目前能否解決部分成本和技術難題？如果可以，太空太陽能可能成為全球能源從化石燃料向綠色能源過渡的關鍵一環。

We already harvest energy from the sun. Its collected directly through what we generally call solar power. This comprises different technologies such as photovoltaics2 （PV） and solar-thermal energy. The suns energy is also gathered indirectly： wind energy is an example of this， because breezes are generated by uneven heating of the atmosphere by the sun.

我們已經從太陽獲得了能量。直接收集自太陽的能量就是人們通常所稱的太陽能，涉及光伏發電和太陽熱能等不同的技術。太陽的能量也可以被間接收集，風能就是一個例子，因為風是由太陽對大氣的不均勻加熱產生的。

But these green forms of power generation have limitations. They take up lots of space on land and are limited by the availability of light and wind. For example， solar farms dont collect energy at night and gather less of it in winter and on cloudy days.

然而，這些綠色發電方式具有局限性。它們占據了陸地上的大量空間，并且受到光和風的可獲得性限制。例如，太陽能發電場在夜間不收集能量，在冬季和陰天收集的能量較少。

PV in orbit wont be limited by the onset of night. A satellite in geostationary orbit （GEO）—a circular orbit around 36，000 km above the Earth—is exposed to the Sun for more than 99% of the time during a whole year. This allows it to produce green energy 24/73.

在軌的光伏發電不會受到夜幕降臨的限制。地球靜止軌道是一條距離地球約3.6萬公里的圓形軌道，在靜止軌道上的衛星一年中99%以上的時間都受太陽照射，因此可以全天候生產綠色能源。

GEO is ideal for when energy needs to be sent from the spacecraft to an energy collector， or ground station， because satellites here are stationary with respect to the Earth. Its thought that theres 100 times more solar power available from GEO， than the estimated global power demands of humanity by 2050.

當需要將能量從航天器傳輸到能量收集器（或稱地面站）時，由于其上的衛星相對地球靜止，地球靜止軌道是理想的選擇。據估計，地球靜止軌道上可獲得的太陽能超過全球人類能源需求預估值（截至2050年）的100倍。

Transferring energy collected in space to the ground requires wireless power transmission. Using microwaves for this minimizes the energy lost in the atmosphere， even through cloudy skies. The microwave beam sent by the satellite will be focused towards the ground station， where antennas convert the electromagnetic waves back into electricity. The ground station will need to have a diameter of 5 km， or more at high latitudes. However， this is still smaller than the areas of land needed to produce the same amount of power using solar or wind.

將太空中收集的能量傳輸到地面需要無線能量傳輸。使用微波傳輸可以最大限度地減少大氣中的能量損失，即使在多云天氣也是如此。衛星發射的微波束將會對準地面站，地面站的天線再將電磁波轉換回電能。地面站的直徑需要達到5公里，在高緯度地區則需要更大的直徑。然而，這仍然比使用太陽能或風能產生同樣電力所需的土地面積要小。

Evolving concepts

不斷發展的概念

Numerous designs have been proposed since the first concept by Peter Glaser in 1968.

自1968年彼得·格拉澤首次提出太空太陽能概念以來，人們已經提出了許多設計方案。

In SBSP， the energy is converted several times （light to electricity to microwaves to electricity）， and some of it is lost as heat. In order to inject 2 gigawatts4 （GW） of power into the grid， about 10 GW of power will need to be collected by the satellite.

在太空太陽能中，能量被多次轉換，從光能依次轉化為電能、微波能，再從微波能轉化為電能，其中部分能量以熱能的形式損失。向電網注入2吉瓦的電力，衛星需要收集大約10吉瓦的電力。

A recent concept called CASSIOPeiA5 consists of two 2km-wide steerable reflectors. These reflect the sunlight into an array of solar panels. These power transmitters， approximately 1，700 meters in diameter， can be pointed at the ground station. It is estimated that the satellite could have a mass of 2，000 tonnes.

近日，“仙后座太陽能衛星”的概念被提出，該衛星由兩個2公里寬的可操縱反射器組成。反射器將太陽光反射到太陽能電池板陣列，這些電力傳送器直徑約1700米，可以朝向地面站。據估計，衛星的質量可能達到2000噸。

Another architecture， SPS-ALPHA6， differs from CASSIOPeiA in that the solar collector is a large structure formed by a huge number of small， modular reflectors called heliostats， each of which can be independently moved. They are mass-produced to reduce cost.

另一種結構“任意大型相控陣太陽能衛星”與“仙后座太陽能衛星”的不同之處在于，它的太陽能收集器是一個由大量名為“定日鏡”的小型模塊化反射器組成的大型結構。每個反射器都可以獨立移動，并且可以通過大量生產而降低成本。

In 2023， scientists at Caltech7 launched MAPLE， a small-scale satellite experiment which beamed8 a tiny amount of power back to Caltech. MAPLE proved the technology could be used to deliver power to Earth.

2023年，加州理工學院的科學家們發射了一顆名為“楓樹”的小型實驗衛星，“楓樹”向加州理工學院傳回了少量的能量，證明該技術可以用于向地球輸送能量。

National and international interest

國內與國際關注

SBSP could play a crucial role to meet the UKs net-zero target by 2050—but the governments current strategy does not include it. An independent study found that SBSP could generate up to 10GW of electricity by 2050， one-quarter of the UKs current demand. SBSP provides a secure and stable energy supply.

太空太陽能可能對英國實現2050年凈零排放目標起關鍵作用，但政府并未將其納入現行戰略。一項獨立研究發現，到2050年，太空太陽能可以產生高達10吉瓦的電力，相當于英國當前需求的1/4。太空太陽能是安全穩定的能源供應。

It will also create a multi billion-pound industry， with 143，000 jobs across the country. The European Space Agency is currently evaluating the viability of SBSP with its SOLARIS initiative. This could be followed by a full development plan for the technology by 2025.

太空太陽能還將創造一個價值數10億英鎊的產業，在英國創造14.3萬個就業崗位。歐洲航天局目前正在通過“索拉里斯”計劃評估太空太陽能的可行性。到2025年，這項技術可能會有一個完整的發展計劃。

Other countries have recently announced the intention to beam power to Earth by 2025， moving to larger systems within the next two decades.

其他國家近日也宣布了到2025年將電力傳輸到地球的計劃，并在今后20年內轉向更加大型的系統。

A massive satellite

巨大的衛星

If the technology is ready， why is SBSP not being used？ The main limit is the enormous amount of mass that needs to be launched into space， and its cost per kilogram. Companies such as SpaceX and Blue Origin are developing heavy-lift launch vehicles， with a focus on reusing parts of those vehicles after they have flown. This can bring the cost of the venture down by 90%.

如果技術已經具備，為什么不使用太空太陽能呢？主要的限制在于需要發射到太空的巨大重量，以及每公斤重量的發射成本。太空探索技術和藍色起源等公司正在研發重型運載火箭，專注于重復使用發射后的火箭部件，這樣可以使發射成本降低90%。

Even using SpaceXs Starship vehicle， which can launch 150 tonnes of cargo into low Earth orbit， the SBSP satellite will require hundreds of launches. Some components， such as long structural trusses-structural elements designed to span long distances-could be 3D-printed in space.

太空探索技術公司的“星艦”火箭可以將150噸物品發射到近地軌道，但即便使用“星艦”，太空太陽能衛星也需要數百次發射。某些部件可以在太空中3D打印，例如長結構桁架這種用于長距離的結構元件。

Challenges and risks

挑戰與風險

An SBSP mission will be challenging—and risks still need to be fully assessed. While the electricity produced is fully green， the impact of the pollution from hundreds of heavy-lift launches is difficult to predict.

太空太陽能任務將富有挑戰性，并且存在仍待充分評估的風險。雖然產生的電能完全是綠色的，但數百次重型運載火箭發射所產生的污染影響難以預測。

Additionally， controlling such a large structure in space will require substantial amounts of fuel， which involves engin-eers working with sometimes very toxic chemicals. The photovoltaic solar panels will be affected by degradation， reducing efficiency over time from 1% to 10% per year. However， servicing and refueling could be used to extend the satellites lifetime almost indefinitely.

此外，在太空中控制如此之大的結構將需要大量的燃料，為此工程師有時會接觸到劇毒的化學物質。由于降解的影響，光伏太陽能電池板的效率將隨著時間的推移每年下降1%到10%。然而，維修保養和補充燃料幾乎可以無限期地延長衛星的壽命。

A beam of microwaves powerful enough to reach the ground could also harm anything that got in the way. For safety， then， the power density of the beam will have to be restricted.

強烈到足以抵達地面的微波束同時會損傷傳輸路線上的一切物體。因此，為了安全起見，必須限制微波束的功率密度。

The challenge of building platforms like this in space may seem daunting， but space-based solar power is technologically feasible. To be economically viable， it requires large-scale engineering， and therefore long-term and decisive commitment from governments and space agencies.

在太空中建造太空太陽能的平臺似乎是一項艱巨的挑戰，但這在技術上是可行的，其經濟上的可行性則有賴于大型工程，因此需要政府和航天機構堅決的長期投入。

But with all that in place， SBSP could make a fundamental contribution to delivering net zero by 2050 with sustainable， clean energy from space.

但當一切準備就緒，作為來自太空的可持續清潔能源，太空太陽能可以為2050年實現零排放做出重大貢獻。

（譯者為“《英語世界》杯”翻譯大賽獲獎者）

1 gain traction流行，受到人們關注。? 2 photovoltaics 光伏發電，縮寫PV，一種利用半導體界面的光生伏特效應而將光能直接轉變為電能的技術。

3 24/7 全天候，指一天24小時一周7天不間斷，讀作twenty-four seven。

4 gigawatt吉瓦，縮寫GW，功率單位，1吉瓦=10億瓦。? 5 其中大寫字母分別代表Constant、Aperture、Solid-State、Integrated、Orbital Phased Array，中文意思為“恒定孔徑的、固態的、集成的軌道相控陣”。? 6英文全稱為Solar Power Satellite via Arbitrarily Large Phased Array，中文意思為“任意大型相控陣太陽能衛星”。? 7加州理工學院，英文全稱為California Institute of Technology。? 8 beam發射（電波）；播送。