Author: Thomas Sattich
In the beginning, Europe’s power system consisted of a limited number of small and isolated power plants in major cities such as Berlin or London. Power transmission at that time can be described as low-voltage, fragmented and limited-area distribution, with steam engines at central points, generating the electricity for a few city blocks, with separate circuits for different customers (e.g. street lamps, workshops). But technical developments such as alternating current systems (a.c.), the transformer and the steam turbine soon allowed high voltage transmission and increasing transmission distances (over hundreds of kilometres) at lower losses and costs.
The original power circuits therefore soon expanded from city centres to the suburbs and beyond. Furthermore, technical standardisation (e.g. on grid frequencies and transmission volts) lead to the development of universal systems which unified not only the circuits of individual power stations into one system, but enabled the interconnection of formerly isolated systems of independent companies to more complex networks; moreover, the growing transmission capabilities allowed to connect consumption centres with distant generation units, such as water power sites in mountain areas or thermal plants near coal mines (Hughes 1983:125-129).
With the First World War came fuel shortages and economic nationalism, resulting in state intervention and support for national power pools that interconnect different power plants in one, closed system (Van der Vleuten, Högselius 2012:81). These developments resulted in a meshed network – or grid – which not only connected a (growing) number of consumers, but also different types of utilities that until then functioned independently (Hughes 1983:262). The resulting power pools therefore did not merely provide the growing supply with a broader range of customers, but allowed individual plants, which formerly operated independently from another, to operate in a power pool, with technically and economically interacting components in one single, interconnected system under common control (Ströbele et al. 2012:234).
Hand in hand with the development of this interconnected power pool, technical and political debates began that largely resemble these of today. Rationalization of the power system is the encompassing topic of these debates – back then and today: These debates have been – and again are – based on the fact that interconnected grids not only encourage the exchange of power between power supplier and power consumer, but between different utilities and supply regions, and therefore allow to maximise the use of the existing generation capacity by taking advantage of local differences in peak load and availability of (e.g. at different times). In other words: Interconnection is a prerequisite for maximal rationalisation and economic use of the existing, capital intensive generation infrastructure.
The advocates of large power systems therefore maintain(ed) that costs per unit decrease with the increase of the physical size of the system and a higher load factor. The early debates about the role of power transmission infrastructure in the Verbundsystem hence resemble today’s debate about decarbonisation in five respects: Power transmission infrastructure allows to rationalise the power system by 1) the optimisation of different characteristics of individual power plants; 2) taking advantage of load diversity and demand factors; 3) centralised control of loads and plants in dispatch centres; 4) by better load forecast; 5) lowering installed and reserve capacity (Hughes 1983:370-371).
Intriguingly, the early debate about power transmission infrastructure and the rationalisation of the power system already saw grid expansion as a means to reduce the use of fossil fuels for generation. Main rationale behind this early debate is the fact that interconnected grids not only encourage power exchange between different utilities in order to maximise the use of the existing capacity, but favour more efficient plants; and since coal not only was a scarce and expensive resource in these days, grid expansion constituted a welcome opportunity for system planners to access the huge and so far largely untapped hydropower resources of mountainous areas that were cheap compared to thermal power plants.
But the integration of hydropower into the expanding grid had other advantages, too: As coal supply was considered unreliable due to numerous coal miner strikes access to hydropower also increased security of supply. Moreover, hydropower works complementary and in a symbiotic relationship with thermal power plants, as hydro can provide base load, while thermal power plants (with their ability to respond rapidly to load changes would largely cover the peak loads and times water is in short supply (e.g. at winter times and summer droughts); by night hydropower stations could lower their flow rate in order to refill their water basins, while thermal power plants cover the lower demand at night.
The realisation that power transmission infrastructure not only enables the interconnection of power generation and power consumers, but that the coupled operation of power plants and the complementary use of energy sources allows to combine the different characteristics of thermal and hydroelectric plants on the one hand, different regions on the other, lead to heydays in the technical planning of the future power system. With growing generation capacities and the capability to transmit electricity over larger distances regional power systems, regional power systems flourished during the interwar period, growing into networks that linked cities, towns, and industrial sites.
With the introduction of the steam turbine electricity became available for a much broader range of customers.
One oft he main difficulties in the realisation of such power pools is the agreement on charges for power exchanges between companies independent in terms of ownership rights.
Reversed roles (hydropower for peak, thermal plants for base load is equally possible).