On 2/16/21 09:49, Michael Thomas wrote:
>
> On 2/16/21 8:50 AM, John Von Essen wrote:
>> I just assumed most people in Texas have heat pumps- AC in the summer
>> and minimal heating in the winter when needed. When the entire state
>> gets a deep freeze, everybody is running those heat pumps non-stop,
>> and the generation capacity simply wasn’t there. i.e. coal or natural
>> gas plants have some turbines offline, etc.,. in the winter because
>> historically power use is much much less. The odd thing is its been
>> days now, those plants should be able to ramp back up to capacity -
>> but clearly they haven’t. Blaming this on wind turbines is BS. In
>> fact, if it weren’t for so many people in Texas with grid-tie solar
>> systems, the situation would be even worse.
>
> You'd think that mid-summer Texas chews a lot more peak capacity than
> the middle of winter. Plus I would think a lot of Texas uses natural gas
> for heat rather than electricity further mitigating its effect on the grid.
>
The difference is that in extreme cold heat pump systems are likely
switching on emergency heat (i.e. plain old resistance heaters) when the
compressor alone can no longer keep up with call for heat demand, which
requires significantly more power. That's never happening in the summer,
which is only ever running the compressor.
Modern air source heat pumps, including air to water units, do not need to fallback to resistance until somewhere in the -4 to -22 degrees F range, depending on ASHP model. That is colder than the lowest lows reported so far in TX during the current polar vortex. Older units from say 30 years ago had significantly higher cutover points. I'm guessing the installed equipment base in TX probably includes a lot of older units.
The difference is while old air source heat pumps were enough to provide all the HVAC needs in moderate temps, modern units can also provide all the heating needs in cold climates like found in Minnesota and Wisconsin, all while maintaining a COP > 1.0, i.e. better than resistance.
Building energy performance also matters. Leaky buildings can expect high energy requirements as the desired interior temperature diverges from the exterior temperature. Well built homes can be heated on nothing more than the output of a regular toaster.
I read that part of the TX issue was a natural gas supply shortfall, where natgas was prioritized to heating applications, leaving electric power generation short. MicroCHP and/or district heating tied into available heat sources (maybe also to datacenter cooling?) would be of great benefit in keeping the lights on and places warm.
The attempts to place blame on renewables are disingenuous distractions away from infrastructural design weaknesses that are being exposed by stressed systems. There are examples of renewables working fine, in colder regions, with high (up to 100%) fractions of energy coming from renewable sources. These systems tend to maximize the use of every available BTU or kWh, and they don't try to solve everything by just throwing more BTUs and kWh at the problem. For starters, there is a relatively simple geothermal system, designed by a man in Nebraska, that allows him to grow citrus: