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Musings of an Energy Nerd

Geothermal Energy and Narrow Streets

Photos from a visit to São Miguel Island in the Azores

The villages on São Miguel are startlingly picturesque. Even the roadside weeds (for the most part, magnificent hydrangeas) are attractive.
Image Credit: Photos by Karyn Patno and Martin Holladay

Everybody seems to love geothermal energy. That’s why many American homeowners brag that they heat their house with renewable energy, saying, “I’ve got a geothermal system that extracts heat from the soil in my backyard.”

Well, I’m sorry to disappoint you, but you’ve been misinformed. You don’t have a geothermal system. All you have is a heat pump that runs on electricity.

Just because the heat-pump salesman told you that it’s a geothermal system, doesn’t mean it is.

A trip to the Azores in Portugal

Karyn and I got married on August 9th. After the wedding, we took a one-week trip together to São Miguel Island in the Azores. We had a fabulous time on our honeymoon. Karyn didn’t even grumble when I took lots of pictures of construction sites and energy installations.

The Azores are located in the middle of the Atlantic Ocean, between Boston and Lisbon. The islands are Portuguese.

On the island of São Miguel, I took a photo of a real geothermal facility — that is, a generating plant that uses boiling water rising from the earth’s hot mantle to drive a turbine that produces electricity. How did I know it was a geothermal plant? Well, I could see small clouds of condensed water droplets emerging from the stacks, and I could see high-voltage power lines leading from the plant down the mountain.

Oh, yes — there was also a sign.

The 173 GWh plant produces 38% of the electricity used on the island of São Miguel. For more information on the plant, see “Use of Geothermal Resources in the Azores Islands.”

Karyn and I came across the geothermal plant while hiking from the hot springs of Caldeira Valha to the crater lake of Lagoa do Fogo.


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  1. homedesign | | #1

    Wonderful Article ... Nice Format
    Hi Martin,
    I appreciate the extra effort spent "weaving" the photographs into the article.
    You wrote: "I could see water vapor being released from the stacks".
    Isn't water "vapor" invisible?
    Weren't you actually observing a "cloud" of condensed water droplets?

  2. GBA Editor
    Martin Holladay | | #2

    Response to John Brooks
    Good catch! I should have known better. I've corrected my slip-up.

    As a student, I was misinformed by a 7th grade science teacher who taught us that steam is invisible, while the correct term for the visible stuff above a boiling teakettle is "water vapor."

    Years later, when I began to study building science, I learned that he was wrong -- but the misinformation still lurks in the back of my brain.

  3. Expert Member
    ARMANDO COBO | | #3

    Why would anyone get married, go on their honeymoon to a great place, jump on a sulfured stinky water just to miss Summer Camp? Where are your priorities?

  4. LucyF | | #4

    Congratulations Martin and Karyn!
    I wondered where you were. We missed you earlier in the month. Sounds like a great honeymoon and educational too.

  5. GBA Editor
    Martin Holladay | | #5

    Response to Armando Cobo
    Sorry, Joe and Betsy (and Armando) -- our week in the Azores was better than summer camp.

  6. jinmtvt | | #6

    congratulations sifu !!
    What made you chose this destination ???

    Est-ce quevous parlez un peu portuguais? assez facile si l'on connait bien le francais :)

  7. GBA Editor
    Martin Holladay | | #7

    Response to Jin Kazana
    Of course we learned how to say "obrigado" and "bom dia" and "cerveja," but I can't claim to speak Portuguese.

    We used ordinary research techniques to choose the destination. The Azores is a very short (direct) flight from Boston -- only 4 1/2 hours -- and is one of the least expensive and easiest-to-reach destinations in Europe for travelers from New England.

    And São Miguel Island is mind-blowingly beautiful.

  8. Expert Member
    Dana Dorsett | | #8

    That's OK...
    ,,, according to some of my Brazilian friends Azoreans shouldn't claim to speak Portuguese either! :-) (Yet somehow they manage to converse...)

    Being able to use geothermal for power generation instead of #2 oil makes island grids almost affordable. Any idea what the retail elecricity rates are like there? Any signs of roofop PV? (Often sign of high electricity prices.)

  9. GBA Editor
    Martin Holladay | | #9

    Response to Dana Dorsett
    I didn't see much evidence of PV.

    According to one online document about Azorean homeowners, "Electricity represents a relatively heavy bill in the families’ budget since more than 80% of the households pay more than 25 Euros per month. The majority (23,2%) spend between 25 and 35€. Between 35 and 45€ accounts for 21,8% while 17,2% spend between 45 and 65€ per month. About 12% [of homeowners] claim to pay over 65€ for electricity per month. The average value of the Azorean electricity bill is approximately 43€."

    See also the graphic below, which I hesitate to take at face value. (The table comes from this source.) The caption makes a confusing reference to feed-in tariffs, and the text of the paper doesn't make clear what this table is showing.


  10. GBA Editor
    Martin Holladay | | #10

    More information on electricity generation in the Azores
    For more information on electricity generation in the Azores, see The Azores and the Renewables.

  11. GBA Editor
    Martin Holladay | | #11

    More on electricity rates
    I found a website that reports that the cost of electricity in Ponta Delgada on the island of Sao Miguel in the Azores is 0.217 euros per kWh.

    That's equivalent to 29¢/kWh.

  12. Expert Member
    Dana Dorsett | | #12

    That's some pricy juice!
    But not atypical of island-grid pricing:

    That's also a price point ripe for grid-defection once the cost of local storage & PV drop just a bit more, if they can't manage to integrate privately owned rooftop PV on their grid. It's definitely sunny enough there to get pretty good return on PV even at today's installed prices if they're allowed to net meter.

    Simple dumb net metering at retail MUST go away someday ( and not in the distant future), but hopefully most regulators will adopt a value-of-solar type approach (similar to Minnesota or Austin TX) so that the baby doesn't get tossed with the bath water. The ultimate resilency value of operating the grid with widely distributed power generation is high, but the details of getting from the incumbent model to Grid v. 2.0.1 will be a bit rocky for awhile. Utility business models and utility regulators are fairly resistant to change, but if they don't they''ll be road-kill once PV hits a buck a watt and storage drops below $200/kwh, when it'll be cheaper for the well-off to just unplug from the grid if the compensation for staying hooked up is too meager (or punitive, as it is in some cases.)

  13. jinmtvt | | #13

    Dana ...
    Please elaborate on what is happening in Minnesota and Austin ??
    I do not understand what you mean.

    Why would net metering and retail need to go away ? What would replace it then ?

  14. wjrobinson | | #14


  15. Expert Member
    Dana Dorsett | | #15

    Value of Solar Tariffs (responce to Jin Kazama, post #13)
    The financial value of distributed solar to the grid operator or other ratepayers varies by where it is on the grid, the amount of power it can be expected to deliver during peak grid-load hours, the costs (both fuel, capital,l and environmental) of the power generation that would that it is displacing, and how much other distributed PV is on both the local & wider grids. In Austin Texas and Minnesota the regulators have agreed upon a method for calculating that value.

    At relatively low penetration rates of PV (say, 2% of all ratepayers having some rooftop solar) the net value to the grid operator can be higher than the flat-rate charged to residential customers. In Minnesota, when a new residential PV system is being installed, the regulators allow the utility to opt whether to use a value of solar tariff (VOS or VOST), a 20 year contracted price for the solar, or whether to simply net-meter at retail. Every year as the penetration of PV in the marketplace increases, the VOS is updated to reflect the new reality, and at some point (probably before 10% and certainly before 15% of all customers having solar) the value of those power inputs will be less than the residential retail rate, at which point the utilities would clearly be using the VOS method for compensating residential PV owners. That isn't necessarily a bad deal for the PV operator- PV is expected to be very cheap in the future, but it protects the non-PV customers from subsidizing the PV owners (who are usually richer than the average electricity customer).

    The approach in MN is based on work done a few years previously to establish a VOST for the publicly owned utility in Austin Texas. It takes quite a bit of careful analysis to strike the right balance- the folks in San Antonio Texas did a perhaps too-hurried imitation of the successful Austin VOST and it pretty much fell flat. In MN stakeholders hashed it out for over a year before it became law earlier this year, and there are still some details being worked out regarding how to compensate "community solar" projects, where homeowner buy a share of a larger PV installation that isn't directly on their roof and behind their meter, and makes greater use of grid resources than a rooftop PV system:

    Most of the utilities currently fighting net-metering are making the argument that paying for PV at the residential retail rate is an unfair cross-subsidy, but almost everyone who has analyzed it in any detail has found the opposite at the current level of distributed PV in the US, but agree that if left in place as a permanent policy it would eventually become a problem (and not just for the profits of the utility).

    When distributed storage accompanies distributed PV the value of the combined resources are potentially even larger, since if properly controlled it stabilizes the grid without requiring infrastructure upgrades on the grid for managing existing or new loads. There is some discussion about developing smart-inverters and allowing the utility to control how much of the PV or battery power to go onto the grid, leveraging the PV/storage owner's capital for the benefit of all ratepayers. This would require re-writing the regulations in most places, but experimental neighborhoods in TX and CA are currently proving the concept. As more PV goes onto the grid and more electric cars, smart-chargers and smart inverters owned by the private parties can become real boon to both the grid operator and other ratepayers, if implemented well.

    With large amounts of distributed generation and modest amounts of grid storage, with some amount of grid-intelligence it's possible to operate micro-grids that can be fairly self-sufficient when the larger grid fails. This makes the grid as a whole more resilient to storm damage or other types of grid failure. With proper adjustments to electric power regulations this can become the new-normal, and it need not be as expensive as a 1-house sized micro-grid (== grid-attached, but essentially off-grid system.) Island grids such as those in the Azores, Hawaii, or Curacao are a prime candidates for developing a rich micro-gridded system, since most island grids have high fuel & capital costs, and high vulnerability to ocean storms, resulting in high retail electric rates.

  16. 33-Machado | | #16

    Your recent trip
    Seriously.....I was born on this island. Amazing coincidence. Thank you for another great article!

  17. GBA Editor
    Martin Holladay | | #17

    Response to Emanuel Machado
    What was the name of the town where you were born?

    São Miguel was stunningly beautiful. We encountered very few tourists during our stay -- except for tourists from the Portuguese mainland. Everyone we met was friendly. I'm amazed that more people don't know what a wonderful place it is to visit -- but then again, it's best to keep quiet, I suppose, so that the Azores remain unspoiled.

  18. BobConnor | | #18

    Will your wife allow?
    Martin, did you wear Speedos when you were in the pool? Did other men wear them since it is in Europe? Will you wife allow them or will she file for a divorce? Dana do you own a Speedo?

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