One of the many challenges facing PV power generation is how to store surplus energy for night time demand. My question is this: since the sun is always shining somewhere on the planet, would it be possible to design an international smart energy grid that can transmit DC current for long distances? Is any research related to this question being conducted?
Asked
Active
Viewed 139 times
2
-
2check out losses in long cables ie due to resistance... – Solar Mike Dec 24 '18 at 23:15
-
2... Take a moment and get out a globe. If you're ambitious, take a marker and lay out where those transmission lines would have to placed for this idea to work. The lines aren't allowed to cross major bodies of water such as gulfs or oceans, and they're not allowed to cross geo-political boundaries. The answer should be pretty self-evident at that point. Every ambitious engineering project has to address those types of challenges. – Dec 25 '18 at 02:36
-
1@GlenH7 They already do both all over the world by the thousands. – Phil Sweet Dec 25 '18 at 03:14
-
Take a look at this set of models for USA regions in 2030. In some cases, you have up to $70.MWh to work with. How far can you transmit a few GW for 70/MWh? diurnal demand price model – Phil Sweet Dec 25 '18 at 03:35
-
@PhilSweet High voltage DC within a region? Sure thing - definitely a been there; done that. High voltage DC across regions and the ocean? That's where politics come into play and derail any technical design. – Dec 25 '18 at 14:34
-
HVDC is easier than conventional AC in every respect, including politics, since there is zero issue of grid compatibility or mutual interation. The restrictions are technical. Just one source and just one sink. No HVDC grid. One political-ish feature of HVDC links to date is that they tend to be designed and delivered by a single contractor. That isn't hard to change if somebody wants to change it. AC distribution started out that way too. – Phil Sweet Dec 25 '18 at 15:11
-
There is nothing too broad about this question. It takes a bit of grunt work to answer, but an average highschool kid could research this. Some wind power can be transported about 1/2 a time zone and still match the LCE of decent primary fossil fuel plants. It can be transported about 2 time zones and compete with modern peaker plants in some areas based on peak prices. Solar isn't in the mix yet. It needs to be attached to the local grid to be competitive. But that doesn't really matter. The ever increasing fraction of low-cost VRE is driving demand for long-range transmisson links. – Phil Sweet Dec 25 '18 at 15:57
-
easier to learn not to run things at night than to rely on someone across the globe who might be seeking an advantage against you. The self-proclaimed wise are very good at playing and wrecking systems. Imagine how easy this would be if we all knew how to accept nightly blackouts! Loss of that ability was the price for using electricity to wreck the day and night system. – Abel Mar 11 '22 at 12:49
3 Answers
0
As stated before in the comments, natural and political challenges let you down to follow this project but electrical engineers and providers face another challenge, look the graph here onder:
the horizontal axis represent time in hour and vertical axis represent power in megawatt. As you can see the irregularities implies having bigger capacity groups than we usually need to provide enough in peak hours.
The cost of bigger capacity made us to find a solution that nowadays is called interconnection electrical networks. The surplus somewhere can compensate for smaller capacity groups somewhere else in peak hours and within some hours later the groups will exchange their role.
A concrete example is France and Belgium in west Europe and Czech and Hungry in east Europe. All the transmission lines are HVDC $400 kV$.
The interconnection follows of course by costs, but it reduce the capital for installation or maybe it prevent the urge for building new power plants, the economical effect of interconnection is strong enough to overpower political problems.
Photovoltaic energy is DC in nature so it means no rectifier or under-station is needed and DC transmission lines can transport 100 % and 50 % more power in respect to 1-phase and 3-phase AC transmission lines. Spare more material and simple transmission towers, no mutual induction and capacitance between wires and ground, all of these advantages push us towards more interconnections.
But do we need it now?
No at this moment we don't.
1- The production capacity of solar or wind power plants are way too small in compare to traditional groups, and this small fraction does't compensate for the start and the maintenance costs.
2- The possible surplus can be transmitted within a small region, for instance San francisco and New York or even closer distance Belgium to Nederland.
3- The most important reason is short circuit detection, grounding and the cost of safety instruments at this moment.
But do we need it later?
Yes and that's why thousands are working together hours and hours each day to overcome all those challenges above.
0
Yes, it is possible to design an international smart energy grid that can transmit DC current for long distances.
The earliest work on this that I'm aware of is from Gregor Giebel and Gregor Czisch, from about 2000. Czisch's thesis, written at Kassel University, was based on his cost-optimisation model looking at the trade-offs between storage, extra generation and long-distance transmission. You can find more about the work - some is in German, some in English - at his website.
HVDC transmission losses are low, of the order of 2-3% per 1000 km.
Since the work of Czisch and Giebel, both PV and wind had dropped in cost significantly, so it's now much cheaper than it was to over-build them both, and curtail when necessary, and that reduces the need for both short-term storage and interconnection.
Nevertheless, there is still a role for long-distance transmission: weather systems get up to about 2000km across, so there is value in having the network span areas larger than that. Chris Clack and Sandy Macdonald did similar analysis for the USA.
And the need for long-term storage is still there. Storage hydro systems are of the right scale for this requirement - Europe has storage hydro which is of the order of 180 TWh, which is the right ballpark. However, it's geographically concentrated in a few places, whereas the need for storage is spread out at continental scale. So a high-capacity continental-scale grid is needed.
The larger the grid, the more climatic systems it spans. And the more climatic systems it spans, the lower the storage requirements for all demand covered by that grid. A grid that spans Europe, the Middle East and North Africa could provide huge benefits to everyone in that area.
410 gone
- 3,751
- 17
- 34
0
There are a quite a few problems that arise from your question. The first that strikes me the hardest is having DC over long distances. This is a huge issue as you will need a super high current and really thick wires. Not to mention the resistance that will come into play due to the cross section of the wires. Most of this can be avoided by using AC, which is why long distance transmission is done via AC.
This is why we have inverters that convert the DC from solar panels to AC. And it is also the same reason why the world has adopted high voltage AC for transmission over DC.
Moving forward, it is technically possible to lay international high tension AC lines, but as someone has mentioned in the comments, there are various geopolitical and economic barriers that need to be overcome. The second problem with this is the actual laying of lines through water. We already have fibre-optics that have been laid across oceans, but they can cause havoc if they get disrupted. Disruptions could be due to one of many reasons including but not limited to terrorists, accidents, natural disasters etc. Having cut fibre optics is quite safe when compared to the havoc that could be caused by cut high tension wires.
It would be better suited for the world to have extra energy storage locally.This greatly reduces reliance on external factors that can't be controlled. It would also be economically cheaper. If the grid on the opposite side of the world faces some issue, you could immediately lose electricity on your side of the globe.
There are numerous problems that need to be solved for this to come to fruition, but this is what is at the top of my head.
gingerbread
- 26
- 1
- 6
-
This answer is incorrect. AC works over reasonably long distances but losses due to resistance, inductance and capacitance make it inefficient. DC is used for long distance transmission because it doesn't suffer from inductive and capacative losses ... which is why long distance transmission is done via DC. – Transistor Nov 06 '22 at 14:43