1.- Comprehensive overview of the project

A state-of-the-art was developed to provide a comprehensive project overview.

D1.2 Comprehensive Overview of the Project

2.- Deploying emerging renewable energies

2.1.- Geothermal energy deployment

The characteristics of geothermal conditions worldwide and in Europe are discussed. The analyses covered the geothermal energy market and identify technologies for geothermal energy recovery, such as direct dry steam plants, flash steam plants, binary cycle power plants, and hydrothermal spallation drilling technology. The report also discusses the use of geothermal energy in mining, including closed-loop and open-loop systems.

Considerations relating to the energy system for geothermal energy deployment in mining areas and the value chain were prepared. These highlight the potential benefits of using geothermal energy, such as reduced costs and emissions, increased energy security, and job creation. The report also discussed the challenges and barriers to geothermal energy deployment, including geological and technical risks, regulatory frameworks, financing, and public acceptance.

This task concludes with a discussion of best practices for geothermal energy deployment in mining areas. It highlights the importance of collaboration among stakeholders, including government, industry, and local communities, and the need for innovative financing mechanisms, such as public-private partnerships, to overcome the barriers to geothermal energy deployment.

D2.1 Geothermal energy deployment

The lessons relevant to GreenJOBS from the deployment of geothermal energy can be summarised as follows:

  1. End-of-life underground coal mines present a unique opportunity for geothermal energy production. These mines have already been excavated to great depths, so they have access to the earth’s natural heat. By repurposing the existing infrastructure, it is possible to create a geothermal power plant that produces electricity and heat with minimal environmental impact, as far as the shaft is close to the potential clients.
  2. Choosing a geothermal technology requires consideration of environmental aspects because the quality of surface waters to which loads of pollutants could be discharged together with industrial sewage or mine water is very low. For this reason, when choosing technologies based on an open-loop system, an environmental analysis should be carried out to limit the negative impact of mine water on the environment.
  3. Geothermal energy is a reliable and constant source of energy that can power homes, businesses, and industries for decades. This makes it an attractive option for countries looking to reduce their reliance on fossil fuels and increase their energy security. Moreover, providing renewable energy, guaranteeing savings in energy costs and maintaining and replacing components, etc., may be attractive to potential consumers.
  4. The process of extracting geothermal energy from coal mines involves pumping water from the mines and using the heat to generate steam, which can then be used to power turbines and generate electricity. The need, in many cases, to pump water regardless of the presence of a geothermal installation helps increase the geothermal project’s financial outcomes, as pump costs can be considered sunk costs.
  5. Due to variations in the quantity of pumped water, temperature and quality, geothermal system mining areas should be selected after a feasibility study. In case of low-quality mine water, installing a heat exchanger inside the underground reservoir in a closed loop system is recommended. If the mine water quality is good, it is preferable to install an open-loop system.

2.2.- Photovoltaic deployment

Photovoltaic technology is one of the fastest-growing renewable energy technologies. However, as any technology, the deployment embeds a number of challenges, boundaries and cons. Difficulties related the lack of raw materials, the increasing prices of PV cells and electronic devices; or related to important requirements to cover, such as land needs, environmental regulations or the “Do No Harm principle”, among others, may lead the depreciation of some investment initiatives.

Thus, a deeper knowledge of such boundaries may help to figure out how to reduce or overcome such difficulties during the project definition, and to define the priorities in the technological development. For example, identifying most appropriate locations where to elaborate consistent viability analysis, adapting the technology to the site. To do that, an exhaustive revision of the different elements conforming a solar PV system is conducted here. Also, main typologies and features of coal mines have been described, defining a generic characterization of such facilities to identify and highlight those singularities of mining areas which could create competitive advantages as potential locations for PV installations.

Taking this into account, two different but complementary scenarios have been identified and drafted as potential use cases. The characterization of these use cases and the definition of specific operational requirements will help to reinforce arguments in favour of using coal mining areas as proper locations of PV systems; but also, to select best technologies to better fit the aforementioned requirements.

D2.2 Photovoltaic deployment

The lessons relevant to GreenJOBS from the deployment of photovoltaic energy can be summarised as follows:

  1. The repurposing of end-of-life coal-related assets and infrastructure at coal mines for photovoltaic (PV) installation plants offers a promising approach for recovering unproductive lands and generating renewable energy.
  2. PV technology is highly modular and ranges in size from small solar home kits to systems with capacity in the hundreds of megawatts, offering a democratised electricity production.
  3. Due to the huge variety of features and types of mine sites, a multi-criteria reasoning analysis should be performed to determine the best technology by scenario.
  4. Leveraging closed coal mines for photovoltaic installation plants presents an opportunity for social, environmental, and economic development while creating new job opportunities in emerging renewable energy sectors.
  5. Aspects like the existence of Interconnection Points could contribute to reduce costs, or timing in executing projects; also, the needs of restoring lands could facilitate permits or licences related to the use of lands for PV projects.

2.3.- Wind power deployment

The wind energy sector is constantly growing and therefore has a positive influence on the European economy. This is reflected in economic growth and the creation of sustainable jobs. As a result, wind energy is particularly popular in research and the optimization of associated processes is constantly being promoted. This includes not only the technology that is used, but also the characterization and distribution of wind energy.

In order to undertake the integration and installation, the associated advantages and disadvantages of this resource are of importance: clean energy, low operating and efficiency costs, as well as high market potential, saving water and creating jobs. The disadvantages in turn are ranging from the specific local conditions, nature and animal protection, the shadow flicker phenomenon and the reliability of the wind resource itself. Apart from that, the demand for rare earths for the production of wind turbines is rising and exceeding existing reserves, while imports and dependencies increase to meet climate goals and a green transition. The planning and approval of such processes are laid down in law. For example, the following aspects must be considered: avifaunistic assessment, noise assessment, shadow assessment, turbulence assessment and geotechnical report.

This report considers the employment effects related to wind energy; the entire value chain of projects for the installation and use of wind power (extraction and processing of raw materials, associated equipment construction and logistics); and project planning and installation. In any case the maintenance and operation, energy delivery, repowering and, after the end of the term, decommissioning and subsequent recycling is needed. Finally, some successful application examples for wind turbines on heaps follow, both in former and still active mining locations. Some of these post-mining examples can be found in Germany, such as the Hoppenbruch heap in the city of Herten in the Ruhr area. However, European heaps largely have one thing in common: their material is often too soft to withstand a superstructure and as a result requires soil improvement and support structures to ensure buildability of wind turbines.

D2.3 Wind power deployment

The lessons relevant to GreenJOBS from the deployment of wind power energy can be summarised as follows:

  1. Russia’s war against Ukraine has exposed Europe’s dependence on fossil fuels and, alongside the climate crisis, poses another important reason for independence through the promotion of renewable energies such as wind power. This needs to be pushed forward as soon as possible, including the former European coalfields for the conversion and new use of closed mines and existing stockpiles.
  2. To achieve the climate goals and the expansion of wind power, an increase in demand of between 2 and 15 times the current level can be expected. Many of the materials needed are, among others, rare earth, which are mainly found in China. Here a 15-fold increase in demand for rare earth, which are irreplaceable for the construction of plants, can be calculated. This already exceeds the availability for the entire EU on the market.
  3. Wind power has many advantages in the assessment: clean energy, renewable resource, operation costs close to zero, cost-effectiveness, technological advances benefit falling prices by 80% since 1980 and are expected to further decrease, development in design optimisation, the market potential is rising, wind power saves water compared to traditional energy production methods, and job growth
  4. Wind power still has some disadvantages: competition when it comes to low costs with other renewable options such as solar power, locations are mostly remote and this makes a supply in urban areas more difficult, reliability of wind itself, wildlife is often disrupted or endangered by rotor blades, disturbance through the average noise level, and the phenomenon of the shadow flicker is disturbing in urban areas.
  5. The requirements for legal planning of wind turbines are avifaunistic assessment, noise assessment, shadow assessment, turbulence assessment and geotechnical report. The geotechnical investigation of spoil heaps has determined that most of them have a common problem: The material is too soft to withstand the superstructure and therefore requires supporting structures and soil improvements through upgrading the spoil heaps and deep foundations.

2.4.- Unconventional pumped hydro deployment

Hydropower in energy generation expansion plays a minor role. However, it has a essential role as an energy storage system, as it can be dispatched when prices are high and, where possible, operated in pumping mode when prices are low. It is an excellent opportunity for Spain, which is on the verge of becoming the first developed industrial country to have a power system dominated by photovoltaic, and to a lesser extent, other non‐dispatchable technologies with zero variable cost, something that starts to be shown in its prices.

Unconventional pumped hydro storage characteristics are presented according to patent nº WO 2019/202456 A1 (2019) that is the property of one of GreenJOBS partners: Magellan & Barents, S.L.: Upper and lower reservoirs within mining embodiments; penstock portions; high-density fluid to be used based on slurry mixtures; surfactants that should be added to prevent freezing of the slurry; etc.

Unconventional pumped hydro storage features in a mining area are pointed out using the example of the Nicolasa mine in Asturias, Spain. Conditions appear extremely attractive for a first‐of‐a‐kind project: Lithology and topography are favourable. A massive formation of quarzitic puddingstone with high strength and low permeability runs for 800 meters along an escarpment. On the other hand, the mining infrastructure allows inspection of the cavern and even rock removal for additional capacity, with existing conveyor belts in working condition. Dense fluid materials are available and can be sourced nearby as the suitability of materials from a nearby coal-washing installation was validated.

D2.4 Unconventional pumped hydro deployment

The lessons relevant to GreenJOBS from this deliverable can be summarised as follows:

  1. When wind power and especially photovoltaic become dominant, their daily generation patterns will induce volatile prices, with a long valley at daylight hours (which happen to be peak hours for power demand) and two price peaks before sunrise and after sunset when PV capacity falls sharply (somewhat paradoxically as both price spikes usually take place when demand is at a minimum).
  2. Photovoltaics and wind power are causing energy storage to become a critical part of the energy transition because photovoltaics and onshore wind power are achieving cost leadership among all power generation technologies. Simultaneously, they depend highly on nature, which is undependable or unreliable at best.
  3. While conventional hydropower systems stabilise the imbalances of supply and demand, which are inherent in photovoltaic and wind power, at the same time, the footprint required by the reservoirs is high. For its part, unconventional pumped hydro storage is directed to a small footprint, a method with high power output as this system uses high-density fluids that allow for a given reservoir or tank volume, an energy storage capacity proportional to the density of the fluid.    

2.5.- Batteries deployment

Diabatic compressed-air energy storage (CAES) is estimated to be the lowest-cost storage technology on an installed cost basis at durations equal to or bigger than 4 hours and 100 MW. Something similar happens with other technologies, such as Pumped storage hydropower (PSH). Indeed, no storage technology different from batteries is used when considering 10 MW.

Li-ion batteries are the most exciting technology. They consist of a battery based on charge and discharge reactions from a lithiated metal oxide cathode and a graphite anode. Lithium-ion batteries are used in various ways, from electric vehicles to residential batteries to grid-scale applications. They have high energy densities, high efficiency and a long life cycle, although with high production costs and require special charging circuits. There are two more commonly used lithium-ion chemistries: Nickel Manganese Cobalt (NMC) and Lithium Iron Phosphate (LFP).

The one selected between NMC and LFP will depend mainly on the price. This aspect is analysed when identifying the best technology for mining areas, as well as the operational requirements of the selected technology.

D2.5 Batteries deployment

The lessons relevant to the Project from this deliverable can be summarised as follows:

  1. Diabatic compressed-air energy storage (CAES) is the most economical energy storage system for 10 hours and 100 MW. It is followed by Pumped storage hydropower (PSH) and Thermal energy storage, predominantly molten nitrate salt. However, other storage media, such as crushed rock, sand, concrete, brick, or cast iron, can be considered.
  2. When requiring energy storage for less than 4 hours and around 10 MW, only batteries are considered and used as feasible energy storage system.
  3. Currently, Li-ion batteries are the most exciting energy storage system to be used for 2 hours and 10 MW. According to the price, Lithium-ion Iron Phosphate (LFP) batteries are the most interesting, as they are more than 10% cheaper than Lithium-ion Nickel Manganese Cobalt (NMC).
  4. The rest of characteristics of LFP and NMC are quite similar: rated power, energy density, efficiency, life cycle, charge/discharge, specific needs, dangers and maturity.

2.6.- Green Hydrogen Deployment

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D2.6 Green Hydrogen deployment