The Kiluea Eruption of 2018 and the Puna Power Plant

I intend to update this post quite a bit, but for now I'm just going to put up this cool Google Maps link showing the lava flow around the Puna Geothermal Power Plant, also known as the Puna Geothermal Venture (PGV)

Link is here.

If you scroll down to the bottom of the left pane, you can choose the terrain view, which will then show the buildings and structures that I discuss below.

Edit 1:

From what I can see, it appears that the lava has covered at least three of the ten production wells at the plant,  KS5, KS6 and KS11 - you will have to zoom in a little to see KS11.  It's not easy to tell which of the wells are actually productive and which are non-producing based on a satellite image, and it's possible that one or more of these wells were inactive even before the eruption.  News articles have mentioned killing wells prior to the lava covering them, so at least one well was productive before it was overrun.
 
Additionally, lava has covered most of the high voltage switchyard, and no doubt has taken out a few of the transmission line towers.

None of this means that the plant has to be abandoned, however.  The cost to correct these issues - assuming the immediate hazard passes - is not that great.  The largest part of the capital expenditure for this type of power plant is the investment needed to drill the wells, and the power station equipment.

It appears that most, if not all, of the power plant is intact.  This is a hybrid geothermal station.  Boiling hot brine is released from the ground under pressure, and allowed to flash to steam in large vessels called separators.  The steam is routed to a steam turbine which drives a generator to make power.

The hot brine remaining in the separator after flashing off steam still contains a lot of heat energy however.  This energy can be extracted by flowing the hot brine through a heat exchanger.  On the other side of the heat exchanger will be a liquid with a low boiling point, such as freon, butane, or propane.   I believe this particular plant uses pentane, as I read they were removing large quantities as the lava approached.

This pentane, boiled off by hot brine in the heat exchanger, can drive a second turbine (or turbo-expander I believe they are called).  This increases power output,  reducing the number of expensive wells required to bring geothermal fluid to the surface.

The plant appears to be made from Ormat units.  These are modular steam and vapor turbine packages that can be stacked together as more wells are drilled and plumbed in.

Below, a small Ormat generator driven on either side by vapor turbines.  They exhaust into the large headers for cooling and condensing by the fans on the platform above.

It shouldn't be a very big deal to get this power station online again after the danger has passed, assuming it suffers no further damage.

Side note - in 1991, while drilling well KS8, it suffered a blow-out.  Here's a synopsis of that event.  I believe they had to evacuate part of the surrounding community due to this event.  Exciting.  And smelly.

6:49 p.m. on June 12, mud pumped up from the bottom of the well released a quantity of hydrogen sulfide gas, prompting several nearby residents to complain. After this small burp, however, conditions seemed to calm down for a while.

About 11 p.m. that night, just before a shift change, the drilling supervisor and another worker, called a tool pusher, left the area of KS-8 to go to their trailers. The driller remained alone on the floor of the rig, “drilling a well that had for almost a week been showing signs of becoming a problem well,” according to a later report. At 11:16 p.m., all hell broke loose. 

The drill had punched through to a fracture in the Earth containing hot (633 degrees Fahrenheit) geothermal fluids under extremely high pressure (up to 1,950 pounds per square inch). The well “kicked” as the fluids shot up the bore hole to the Earth’s surface. Residents in the surrounding area were jarred awake by the unmuffled roar caused by the steam shooting out the well – a sound likened to what one hears standing at the end of a runway when a jet taking off.

Concentrations of hydrogen sulfide (the acrid smell of rotten eggs, noticeable by humans when it is in concentrations as low as 3 parts per billion) rose into the parts-per-million range in some areas. WellKS-8 continued its venting for the next 31 hours. For the next four months, the underground blow-out resisted control. It was not successfully plugged until September, when PGV announced that the well had been “killed.