For the last five years, copper has taken something of a backseat in the mining industry from an investment perspective. Precious metals like gold and silver have dominated speculative capital inflow and a large number of companies operating in these latter two resource spaces have appreciated in line with the price of the underlying assets.

Recently, however, copper is once again finding its footing and could represent a considerable opportunity for early movers that want to pick up an exposure to the next wave of copper growth. The trend towards green energy, driven by electric vehicle (EV) adoption and the rise in the use of the lithium-ion battery over more traditional fossil fuels is going to boost demand for copper over the next 30 years considerably. EV's use up to three times as much copper in their construction as do standard internal combustion vehicles. Lithium batteries require cobalt, which is a byproduct of the copper extraction process.

Companies operating the space (i.e. copper miners) look set to increase in valuation in line with the expansion in demand for copper over the period. With this in mind, here are two companies that might make for a rewarding exposure to this growth.

The two companies in focus are US Gold Corp (Nasdaq:USAU) and OZ Minerals Limited (ASX:OZL).

Let's kick things off with US Gold Corp.

As its name suggests, US Gold Corp. isn't a pure play copper exposure – the company is also a gold mining and exploration company. It's based in the US, headquartered in Nevada, and has an operational focus in both Nevada and Wyoming. It's the latter of these two states that is of interest here, with US Gold Corp.'s Copper King being the property that qualifies it for a position on this list.

The property is located in the Silver Crown mining district of southeast Wyoming, approximately 20 miles west of the city of Cheyenne, on the southeastern margin of the Laramie Range. In total, Copper King comprises about 1,120 acres that include two Wyoming State Mining Leases.

The project has a relatively rich development history, with early exploration and mining dating back to the late 1800's and, since 1938, at least nine historic drilling campaigns by at least seven companies plus the U. S. Bureau of Mines having been conducted on-site. In total, these campaigns have translated to 91 drill holes totaling 37,500 feet, with all but six of these drill holes within the current resource area.

These historic drilling programs highlighted a degree of potential at the site but the real insights derived from a 2012 updated technical report, prepared in accordance with National Instrument 43-101 by Mine Development Associates. From this report, markets learned that Copper King contains 59.75 million tons of measured and indicated mineral resources with average grades of 0.015 ounces/ton Au and 0.187% Cu. This amounts to approximately 926,000 ounces of gold and 223 million pounds of copper. An extra 15.62 million tons of inferred mineral resources with a slightly lower average grade of gold but a slightly higher average grade of copper adds 174,000 ounces of the former and 63 million pounds of the latter to the equation.

With these sorts of technical reports, it is possible to produce a base-case estimate as to the net present value (NPV) of the project in question. Based on a $1100 per ounce cost of gold and a $3 per pound cost of copper, the Copper King Project will generate Net Cash Flow of $273.7 million and the Project has an NPV of $159.5 million at a 5% discount rate.

For reference, US Gold Corp. currently trades for a market capitalization of just $26 million – one-sixth the implied NPV of its Copper King project.

A magnetic survey map just hit press (available here) and the map confirms the resource volume and location as implied by the above-discussed report. Right now, management is compiling historic drilling data in an attempt to bring it up-to-date ahead of what should be a major catalyst for the company at Copper King – the initiation of a Strathmore (the latest and most advanced exploratory drilling method) drilling campaign and, beyond that, resource extraction.

Drilling is expected to start before the end of 2017, making the above-noted catalyst a potential near-term driver for US Gold Corp.

Moving on, let's look at OZ Minerals Limited (ASX:OZL).

This one is a different sort of exposure in that the company is an Australian entity as opposed to a US-based mining company but it is very much a copper play and recent news both makes it one to watch right now and qualifies it for this list alongside US Gold Corp.

Many reading might already be familiar with OZ Minerals, it's one of the largest copper companies in Australia (outside of the handful of behemoths like BHP Billiton Limited (ASX:BHP) and it already generates substantial revenues on its active resources in that nation. During 2016, the company reported revenues of $822 million and produced 116,000 tons of copper.

The company's latest announcement, however, and the announcement that – as mentioned – qualifies it for inclusion here, looks set to add to this production volume considerably. 

Specifically, OZ Minerals just reported that its board has approved the building of a $916 million copper mine in the northern part of the state of South Australia. The project will have a full-time workforce of 500 and will be the second largest copper mine in South Australia, behind BHP’s Olympic Dam.

The mine that Oz intends to operate in the region is called Carrapateena and the company has spent the last 12 months building what it calls the Carrapateena decline (with decline here just being another word for mineshaft) at the site. The decline includes more than 2.5 km of tunnels and is a sort of precursor to phase I of the larger construction project, which construction of enabling infrastructure including the accommodation village (for the workers) and an airstrip, as well as continuing development of the dual access decline.

Which brings us to the catalyst – construction initiation. As per management's latest report, Oz Minerals expects to begin phase 1 at some point during September 2017. Beyond that, leasing and permitting should come during 2018 (likely late-2018) and the company is targeting production initiation during 2019. That's a pretty tight timeframe, but it's one that we have seen OZ Minerals hit in the past so there's nothing to suggest it won't be adhered to.

Last month, management reported that OZ Minerals had $625 million in the bank at the end of the financial year and could afford to fund the mine itself, removing any dilution risk near to medium term. At peak, the Carrapateena mine is expected to produce 65,000 tons of copper and 67,000 ounces of gold per year.