If you are given a thousand guts, you may not dare to think that the construction of a 3,800-kilometer-long strange power transmission line to send electricity from the Sahara Desert in Africa to Britain in northern Europe through the seabed is not inter-provincial and transnational, but intercontinental power transmission, is this pure delusion?But the British just dared to think about it, and included it in the national priority infrastructure project, and Morocco on the other side has also expressed its support for the plan, which may be a $25 billion project, which may be gradually becoming a reality.
The plan comes from a company called Xlinks, which envisions the construction of a 200-square-kilometre solar photovoltaic farm in the arid Qalmin-Nong region of Morocco, Africa, plus a large wind farm that generates electricity from sunrise to dusk, which is then stored in a 5 gigawatt energy storage facility, which is then transported via a high-voltage direct current (HVDC) transmission (HVDC) cable from Portugal, Spain, The seabed near France, which is transported to Devon, England, 3,800 kilometers away, is expected to be completed in 2029 and meet 8% of the UK's electricity needs.
The reason why I want to say strange is because the 3,800-kilometer-long power transmission line can be said to be unheard of, so can it be realized?
According to Xlinks' plan, the cables will be laid under the continental shelf in Europe, about 700 meters from the seabed, and the cables will need to be reinforced to withstand 70 atmospheres, which may not be a problem, as there are already similar submarine transmission cables in the world, such as the North Sea Link (NSL) between the United Kingdom and Norway, which is 720 kilometers long and will be put into operation in 2021;The 765-kilometre Viking line between the UK and Denmark is expected to be electrified in JanuaryThe Eurasian interconnection line from Israel to Greece, which is 1,208 kilometers long and the lowest point is located at the bottom of the sea at 3,000 meters, has started construction in 2022 and is expected to be completed in 2027.
So technically, the biggest uncertainty may be the transmission distance of 3,800 kilometers, so is there a precedent for such a thing now?
What we just said is the submarine cable, in fact, on land, there have already been nearly 3,800 kilometers of transmission lines, this is the UHV DC transmission system from Xinjiang to Anhui completed in 2019, with a total length of 3,293 kilometers, a rated voltage of 1100kV, a transmission capacity of 12GW, and a total investment of 40.7 billion yuan.
So from this point of view, 3800 kilometers should not be much of a problem. Many people may be curious, why not use alternating current?Isn't it all alternating current that is used now?
In fact, the current ultra-long-distance transmission can only be transmitted by high-voltage DC, because the DC transmission investment is less, the loss is lower, and the ultra-long-distance transmission, due to the characteristics of alternating current, is basically unrealizable.
The first is that the cost is lower. In the case of the same power, DC transmission can save 1 3 wires than AC transmission, and the tower is simpler, coupled with the AC skin effect, that is, the closer to the surface of the wire, the greater the current density, the resistance increases, the loss increases, and the cross-sectional area of the wire must also be increased, in general, the cost of 1 3 to 1 2 will be saved.
And then there's less loss. Since direct current only transmits active power, while alternating current transmits active power and reactive power at the same time, the loss of alternating current is greater, generally speaking, the loss of direct current transmission is 3. per 1000 km5% or so, while alternating current is going to nearly double to 67%。
The most fatal problem is actually the capacitive effect, which makes DC transmission useless under the sea and underground. This is because in the case of AC transmission under the sea or underground, the core wire is wrapped in an insulating layer and a metal jacket, which will exhibit high capacitance characteristics, which is equivalent to a long coaxial capacitor, and there must be additional current to charge this capacitor, resulting in increased heat loss, increased temperature, and excessive distances may even lead to short circuits and burn the cable. The capacitance of a DC cable is only charged when it is first energized or when the voltage level changes, and does not require additional current, so it does not cause heat loss and heating up, making it more reliable and efficient.
In addition, DC transmission can also be interconnected between AC systems of different frequencies and asynchronously, and new energy power generation is directly connected to AC systems, but there are also shortcomings such as relatively complex technology, high cost of converter stations and limited overload capacity, and reduced reliability and availability caused by additional conversion equipment.
Nevertheless, from the above analysis, we can actually see that if the UK is to build this 3,800-kilometer submarine transmission cable, it should be technically feasible, and the economic, political and social issues may be more challenging. In fact, there is an even more ambitious project in the southern hemisphere, which is the Australia-Asia Power Link (AAPowerlink), which is 800 kilometres of onshore cables, 4,500 kilometres of submarine cables, and up to 20 gigawatts of power generation, with a total investment of A$35 billion to transport solar power from Australia's Northern Territory to Singapore.
However, at the beginning of this year, due to a new round of financing conflicts, the two major shareholders broke up, causing it to enter the state of trusteeship.
So on the whole, although the British project seems to be wonderful, with the development of the global new energy strategy and transmission technology, the feasibility should not be too much of a problem, and the biggest problem is more likely to be a matter of money.