Power-to-Gas

Renewable Hydrogen Economy for the Energy Transition

Méziane Boudellal

• Publisher: De Gruyter
• Year: 2018
• eBook ISBN: 9783110558890
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Chemistry
• Index: Chemistry

With the development of renewable electricity and the expected important surpluses of production, how can the use of hydrogen improve the green energy portfolio? Power-to-Gas covers the production of hydrogen through electrolysis and its storage or conversion in another form (gas, chemicals or fuels). It emphasises the need for new technologies with global energy consumption, markets, and logistics concepts. Pilot projects around the world are discussed as well as how policy and economics influence the real use of these energy harvesting and conversion technologies.

1Global energy consumption

In recent decades, there has been a significant increase in global energy consumption in virtually all sectors, led by the so-called emerging countries such as China and India. Non-renewable sources of energy, which are still predominant, lead to increasing pollution, nuisances and greenhouse gas levels. Faced with the consequences on the population, fauna, flora and climate, it is necessary to turn to renewable energies.

One of the factors to be addressed before defining the potential of power-to-gas technology is the overall energy consumption, its evolution and the associated technical challenges (production, distribution and storage).

1.1Strong growth in energy demand

The overall increase in prosperity leads to an increase in energy requirements, whether for transport, industry, tertiary or residential sector. The evolution of the gross national product is an indicator of the energy consumption, although there remains a factor of uncertainty on the relation between these two parameters, whose projections for the next decades try to predict by studying several scenarios.

1.1.1Evolution of total energy consumption

Data for recent decades show a steady increase in consumption (Figure 1.1), even if it is weighted by climatic variations or economic crises.

This energy comes from different sources: Non-renewable sources such as oil, coal, gas and uranium, and renewable sources such as wind, solar and hydropower. The contribution of each of these sources also varies from country to country (Figure 1.2).

A comparison of consumption trends shows that for many countries there is a tendency towards a decline or stabilisation of primary energy consumption (Figure 1.3) in recent decades. However, this does not mean that consumption by energy type or sector has also declined or remained stable, as shown in Chapter 2.

1.1.2Energy storage

While solid or liquid fuels can be stored in large volumes, electricity can only be stored for small quantities in relation to production and consumption for technical (mainly relatively low capacity of available systems) and financial (high costs per kilowatt for some solutions such as batteries) reasons. Electricity storage therefore remains very limited in relation to consumption (Table 1.1) or production capacity.

Figure 1.1: Global gross energy consumption in Mtoe (BP Statistical Review of World Energy 2016).

Figure 1.2: Contribution of different energy sources in Germany, China and the USA in 2016 (Data: US Energy Information Administration, AGEB (Germany), BP Statistical Review 2017).

The actual storage capacity of electricity is out of proportion in relation to production capacity or consumption when compared to that of natural gas or stored petroleum products. In the USA and China, the capacity of electricity storage accounts for about 2–3% of production capacity, with Japan being an exception, which is close to 9%. One could certainly include some of the hydropower plants as “latent” electricity, but they cannot be really considered as storage.

Figure 1.3: Comparative changes in primary energy consumption.

Table 1.1: Electricity storage capacities (Data: BP Statistical Review of World Energy 2016; BMWI, Germany; RTE, France).

Security stocks for oil, petroleum products and gas

Each country stores gas and crude oil or petroleum products to meet either significant demand or a shortage. The IEA (International Energy Agency) is requesting and the European Union imposes, for example, a minimum stock of 90 days of net imports of petroleum products.

In China for 91 million barrels of storage in 2014, the daily consumption was 10.7 million barrels per day, meaning nine days of consumption only. The goal of the Chinese government is to have a storage capacity of 500 million by 2020.

For natural gas, the USA in 2016 had a maximum storage capacity corresponding to 62 days of consumption and Germany theoretically has 100 days of reserves against 20 days maximum for the UK.

Unlike the storage of electricity, gas, liquefied natural gas (LNG) and oil or petroleum products stocks allow an autonomy of up to several months (Table 1.2 – storage capacities are the maximum volumes and not necessarily those stored). The actual volumes in reserve vary according to management strategies, market prices (e.g. purchases when prices are low) and level of consumption in relation to production or import.

Table 1.2: Maximum storage capacity in millions of tonnes (Data: BP Statistical Review of World Energy 2017).

By the end of 2014, China had a storage capacity of 17.7 billion m3 of natural gas (with 3 billion m3 in stock) and 37 million tonnes of LNG (with 20 million tonnes in stock). The maximum capacities of these reserves as well as the quantities stored are also constantly changing, in view to ensure energy independence from potential risks (conflicts, high prices etc.).

1.1.2.1Electricity peak load

The management of peak loads (Figure 1.4) is critical for electricity suppliers. It depends mainly on the use of this electricity. Electrical heating is still widespread in some countries and, at very cold temperatures, demand is rapidly increasing. Electricity providers must be able to respond to them without delay. They have to balance real-time production and consumption and instantly smooth out these peaks.

Figure 1.4: Example of peak consumption.

In case of demand greater than production, the low capacity of the electricity storage units requires either the use of imports if possible or run gas-fired power plants with a very rapid start-up time.

1.1.3Consumption by sector of economy

Among the different sectors of the economy (housing, tertiary, industry, agriculture, transport), changes in energy consumption in recent years have experienced different trajectories. While in the long-standing industrialised countries (USA, Japan, UK, Germany etc.), the industry has been able to reduce its consumption, transport, residential and tertiary, have seen a steady increase in consumption in recent years, only modulated by climatic variations (e.g. a mild winter reduces heating consumption whereas a hot summer leads to an increase in the electricity consumption due to air conditioners). China does not yet show such a trend: It still has a very intensive energy industry (Figure 1.5).

Gross...

Table of contents

• Cover
• Title Page
• Copyright
• Dedication
• Foreword
• Contents
• Introduction
• 1 Global energy consumption
• 2 Electricity of renewable origin
• 3 Principle of power-to-gas
• 4 Electrolysis
• 5 Power-to-gas strategies
• 6 Beyond power-to-gas
• 7 Power-to-gas experiments
• 8 Financial approach to power-to-gas
• 9 Role of power-to-gas in energy transition
• Acronyms
• Index