In his February 15 column in Diario Estrategia, the professor and director of the UAI’s Master’s in Energy and Environment program highlighted SERC’s contribution to the development of solar energy nationwide.
Column
Chile Can Lead the Development of Solar Thermal Technologies by Adding Value to Its Strategic Minerals: Lithium and Copper
The growing integration of renewable energy sources into the country's energy mix is recognized as one of Chile's top priorities for harnessing its solar, wind, geothermal, and other energy potential.
Monday, February 15, 2016, 10:33 a.m.
Lithium has a high thermal storage and transfer capacity, and copper is an excellent heat conductor; therefore, the use of both materials in any thermal system—especially solar thermal systems—would, in principle, be highly beneficial, as it could improve efficiency, lower costs, and also provide new added value to our strategic minerals by opening up new markets for associated materials, products, and components.
It is well known that Chile possesses more than 60% of the world’s known lithium reserves, is the world’s leading copper producer, and has one of the highest solar energy potentials on the planet. With regard to materials, our country has designated lithium as a strategic mineral, and copper is also considered strategic due to its obvious importance to the national economy, contributing approximately 10% of our GDP according to figures from the Mining Council. Despite these encouraging figures, our country must ensure sustainable development to avoid relying exclusively on market fluctuations. Sustainable development requires transforming resources into other forms of wealth, such as buildings, machinery, new materials, and human capital. Following this sustainability approach, certain assessments can be made to determine whether it is technically and economically feasible to convert the country’s lithium reserves and available copper into competitive energy produced in the same region where these metals are extracted, thereby benefiting local communities and the region as a whole.
The growing integration of non-conventional renewable energy sources (NCRES) into the country’s energy mix is recognized as one of Chile’s top priorities for harnessing its solar, wind, geothermal, and other energy potentials. The Paris Climate Summit (COP 21) has highlighted the significant role that renewable energy will play in the world’s energy future, and in Chile’s specific case, it has been established that solar energy will lead this development, giving rise to important initiatives such as CIFES-CORFO’s “Strategic Solar Program” (http://cifes.gob.cl/programas/programa-estrategico-solar/), CONICYT’s “Solar Energy Research Center” (SERC-Chile, sercchile.cl/), and by supporting the establishment of centers of excellence such as Fraunhofer and Laborelec.
One of the biggest and most important challenges that these national initiatives—and all countries in general—must address is the intermittent nature of solar energy, which makes it difficult to match energy supply with demand. In particular, for concentrated solar power (CSP) plants, Thermal Energy Storage (TES) is considered a key alternative that allows plants to operate when solar radiation is unavailable, increasing the plant’s capacity factor from a range of 20% to 25% without a TES system to 40% to 50% with 6 to 7.5 hours of TES. In fact, Chile is preparing to host a new solar thermal power plant with a capacity of 110 MW, which will feature an advanced storage system allowing it to operate at a capacity factor of 80% and generate electricity for up to 17.5 hours without sunlight. The primary TES material in CSP plants—and, in some technologies, also the heat transfer fluid (HTF)—is a liquid or molten salt composed of 60% NaNO₃ and 40% KNO₃, also known as “solar salt,” which is kept hot at temperatures above its melting point of 223 °C. Chile is also the world’s leading producer of this material. It is worth noting that these TES and HTF materials can always be improved, and significant research efforts are already underway worldwide to develop new, more efficient materials that will help reduce costs. First, the development of new materials with lower melting points for use as TES and HTF is a key challenge, as this will prevent, for example, blockages caused by solidification in pipes below the melting point, as well as expenses related to energy self-consumption and other CAPEX and OPEX costs. In this context, some recent preliminary studies on thermal materials for CSP (http://www.mdpi.com/2071-1050/8/2/106/htm) are available, such as those conducted by researchers Macarena Montané, Shahriyar Nasirov, and Raúl O’Ryan at Adolfo Ibáñez University (UAI), which show that salt mixtures containing lithium nitrate may be a potential alternative to address the risk of solar salt solidification in dual-tank TES systems, potentially reducing their levelized cost of energy (LCOE) by up to 4% and improving system efficiency due to lithium’s high energy density.
Furthermore, since materials with higher energy densities reduce the amount of storage material required, latent heat storage using solid-to-liquid phase-change materials (PCMs) has also been identified as a possible alternative for improving TES systems. These PCMs have low thermal conductivity, which results in a decrease in the heat transfer rate and energy utilization efficiency. In particular, copper, which has high thermal conductivity, is considered one of the most suitable and promising materials for heat transfer. Some studies have already been conducted showing that, for example, copper sponges [1] and copper-encapsulated PCMs [2] could be a good solution; however, their manufacturing costs must still be reduced, as they are currently not economically viable for implementation.
In conclusion, lithium and copper are very promising materials, and we are on the right track to achieve significant development in the thermal and solar industries; however, to succeed, we must never waver in our support for and interest in innovation.
Gustavo Cáceres
Director of the MCI in Energy and the Environment, UAI
