Question

Abandoned lead mines near Park Hills, Missouri are filled with an estimated \(2.5 \times 10^{8} \mathrm{~m}^{3}\) of water at an almost constant temperature of \(14^{\circ} \mathrm{C}\). How might this resource be exploited for heating and cooling of the town's dwellings and commercial buildings? A newspaper article refers to the water-filled mines as a free source of heating and cooling. Discuss this characterization.

Short answer

The water in the mines can be used as a heat source in winter and a heat sink in summer through the use of heat pumps. This can be energy-efficient, although there are initial infrastructure costs.

Step-by-step solution

- Understanding the Problem

The problem involves determining how the water in the abandoned lead mines can be used to provide heating and cooling to the town.

- Identify the Properties of the Water

The water in the mines has a constant temperature of 14°C. This means it can absorb or release heat when there is a temperature difference with the surroundings.

- Heating in Winter

During winter, the outside temperature is lower than 14°C. By using a heat pump, heat can be extracted from the water and transferred to the buildings, using the water as a heat source.

- Cooling in Summer

During summer, the outside temperature is higher than 14°C. The same water can be used as a heat sink where the heat pump can transfer excess heat from the building to the water, providing cooling.

- Energy Efficiency

Using the water from the mines for heating and cooling can be more energy-efficient than traditional methods. Heat pumps typically have a high coefficient of performance (COP), which makes them effective for this application.

- Discussion on Free Resource

While the water itself is free, exploiting this resource would still involve costs for infrastructure such as installing heat pumps and maintaining the system. However, the operational cost savings and environmental benefits make it an attractive option.

Key concepts

Heat Pump

A heat pump is a device that transfers heat from one place to another. In the case of the abandoned lead mines in Park Hills, Missouri, the water at 14°C can serve as a source or sink for heat transfer. During winter, the pump extracts heat from the mine water and transfers it to the buildings for heating. Conversely, in summer, it extracts heat from the buildings and releases it into the water, keeping the indoors cool.
This process is efficient because the constant water temperature of 14°C provides a stable environment for the heat pump to operate. The heat pump's ability to move heat rather than generate it allows for significant energy savings.

Energy Efficiency

Energy efficiency is about using less energy to achieve the same outcome. Heat pumps exemplify efficient use of energy.
Their high coefficient of performance (COP) means they can transfer more heat per unit of electricity compared to traditional heating methods. This is particularly true in the context of the lead mines, where consistent water temperature optimizes the pump's performance.
Using such systems can reduce the reliance on fossil fuels and decrease greenhouse gas emissions.

• In winter, heat pumps draw less electricity by using the relatively warmer mine water.
• In summer, they offer cooling by expelling heat into the stable-temperature mine water.

This dual capability underpins their energy-efficient nature.

Renewable Resources

Renewable resources are natural assets that can be replenished. The water in the lead mines, while not traditionally classified as a renewable resource, functions similarly due to its ability to absorb and release heat repeatedly without depleting.
This makes it a sustainable option for heating and cooling. Tapping into such unconventional resources can reduce strain on conventional energy sources and promote environmental sustainability.

• Using mine water leverages a naturally occurring, constant temperature.
• This reduces the need for generating new energy, leveraging an existing resource creatively.

Such innovative uses of available resources reflect a growing trend towards sustainable engineering and energy practices.