• Walney farm off Cumbria, opening today, is world's largest • Move seen as clear pro-renewables gesture amid scepticism • Britain 'number one destination for investment in offshore wind'

The new energy secretary, Lib Dem MP Ed Davey, will face down the growing army of renewable power critics inside the coalition by making his first major outing a visit to a wind project.

He will open the world's biggest offshore windfarm on Thursday – the £1.2bn Walney scheme, off Cumbria, with more than 100 turbines generating enough power for 320,000 homes.

Davey said: "Britain has a lot to be proud of in our growing offshore wind sector. Our island's tremendous natural resource, our research base and a proud history of engineering make this the No 1 destination for investment in offshore wind.

"And Walney is the newest, biggest and fastest-built jewel in that crown, providing clean power for hundreds of thousands of households.

"Opening Walney during my first week in office lets me underline my commitment to continuing the coalition's work to make this sector a success story for the British economy, not least with the innovation it is driving and the employment it is creating."

It comes after 100 Conservative MPs wrote to David Cameron at the weekend calling for renewable energy subsidies to be cut – although their main concern was onshore turbines, which they accused of wrecking the countryside.

British power company SSE and Denmark's Dong Energy say that Walney breaks a number of records: it has been built more cheaply and quickly than previous schemes, and has been supported by foreign pension funds.

Anders Eldrup, chief executive of Dong, the largest power company in Denmark and operator of the farm, said: "It marks a new era in terms of financing, being the first project in the UK backed by institutional investors. Walney is a landmark in offshore wind and [in] Dong Energy's strong drive to further industrialise offshore wind power and cut costs."

The new 367.2MW scheme, which will itself be dwarfed by the massive London Array off Kent when that eventually comes on-stream, is made up of two projects, Walney 1 and 2, off Barrow-in-Furness.

The company claims the second part of the scheme was the quickest-built of its kind, with all turbines and cables installed in less than six months, and that it has achieved considerable cost reductions at a time when critics claim offshore wind is too expensive.

The estimated £70bn outlay that is needed to greatly expand offshore wind capacity – the so-called "round three" of windfarm construction – is seen as dependent on attracting new forms of financing, so SSE and Dong are keen to trumpet their success at Walney.

OPW – a consortium of the Dutch pension fund PGGM and the energy investment fund Ampere Equity Fund – took a 24.8% stake in the project in December 2010, joining majority owner Dong Energy (50.1%) and SSE (25.1%).

"The partnership with PGGM and Ampere clearly demonstrates that institutional investors are willing to invest in well-structured offshore wind projects alongside market leading industry players," said Eldrup.

Dong has around 30% of the offshore wind market throughout Europe and is regarded as a pioneer among utilities for its willingness to throw its weight behind renewables. The company has in the past taken 85% of its power from coal or oil and 15% from green sources, but Eldrup said he was determined to completely "twist" this around to 85% renewable and the rest from gas.

"We are targeting 50/50 by 2020 and I expect we can get there before then," he said.

Dong is also an investor in the London Array – scheduled to bring its 630 turbines on stream by the end of this year – and is pioneering deepwater gas projects off the west of Shetland, working alongside Total of France.

The stance Davey takes at the energy department is seen as important at a time when the renewable industry is under pressure as governments throughout Europe cut back public spending. Chris Huhne, who resigned from the energy brief last week facing criminal charges over a driving incident, was a very vocal supporter of wind energy in a coalition government containing many sceptics. The less experienced Davey will be under pressure from environmentalists to show he is willing to take a similar stand.

He got off to a good start in the eyes of Greenpeace by making his first ministerial visit to a home energy efficiency centre last week in Watford.

On Wednesday, Davey launched a new offensive on energy wastage, with the creation of a dedicated team within the energy department to spearhead energy efficiency policy and make it more relevant to people's everyday lives.

He announced details of the new Energy Efficiency Deployment Office (EEDO) at a meeting with industry leaders at the John Lewis Partnership's Peter Jones store in Sloane Square, London.

In his first speech as secretary of state, Davey said: "I'm hugely enthusiastic about energy efficiency. It's the cheapest way of cutting carbon – and cutting bills for consumers. It has to be right at the heart of what we do.

"EEDO will be a centre of expertise, challenging our work and making energy efficiency real and relevant to people's everyday lives. Two out of three consumers think their home is wasting energy, but only one in three is going to do anything about it. That has to change. We need to get out there and show people what energy efficiency can really do for them."

• This article was amended on 9 February to correct the capacity of the Walney offshore wind farm